7 research outputs found
Molecular states and spin crossover of hemin studied by DNA origami enabled single-molecule surface-enhanced Raman scattering
The study of biologically relevant molecules and their interaction with external stimuli on a single molecular scale is of high importance due to the availability of distributed rather than averaged information. Surface enhanced Raman scattering (SERS) provides direct chemical information, but is rather challenging on the single molecule (SM) level, where it is often assumed to require a direct contact of analyte molecules with the metal surface. Here, we detect and investigate the molecular states of single hemin by SM-SERS. A DNA aptamer based G-quadruplex mediated recognition of hemin directs its placement in the SERS hot-spot of a DNA Origami Nanofork Antenna (DONA). The configuration of the DONA structure allows the molecule to be trapped at the plasmonic hot-spot preferentially in no-contact configuration with the metal surface. Owing to high field enhancement at the plasmonic hot spot, the detection of a single folded G-quadruplex becomes possible. For the first time, we present a systematic study by SM-SERS where most hemin molecule adopt a high spin and oxidation state (III) that showed state crossover to low spin upon strong-field-ligand binding. The present study therefore, provides a platform for studying biologically relevant molecules and their properties at SM sensitivity along with demonstrating a conceptual advancement towards successful monitoring of single molecular chemical interaction using DNA aptamers
Poly-N-isopropylacrylamide colloidal arrays as templates for droplet-assisted fabrication of plasmonic nanostructure patterns
Poly-N-isopropylacrylamide colloidal arrays are exploited for site-selective self-assembly of gold nanoparticles on large areas. The soft colloids host the drying process of gold nanoparticle dispersion droplets and leave room for capillary convection and Marangoni convection flow paving the road to a simple bottom-up fabrication strategy for nanostructure arrays
Photothermomechanical Nanopump: A Flow-Through Plasmonic Sensor at the Fiber Tip
Optical fibers equipped
with plasmonic flow sensors at their tips
are fabricated and investigated as photothermomechanical nanopumps
for the active transport of target analytes to the sensor surface.
The nanopumps are prepared using a bottom-up strategy: i.e., by sequentially
stacking a monolayer of a thermoresponsive polymer and a plasmonic
nanohole array on an optical fiber tip. The temperature-dependent
collapse and swelling of the polymer is used to create a flow-through
pumping mechanism. The heat required for pumping is generated by exploiting
the photothermal effect in the plasmonic nanohole array upon irradiation
with laser light (405 nm). Simultaneous detection of analytes by the
plasmonic sensor is achieved by monitoring changes in its optical
response at longer wavelengths (∼500–800 nm). Active
mass transport by pumping through the holes of the plasmonic nanohole
array is visualized by particle imaging velocimetry. Finally, the
performance of the photothermomechanical nanopumps is investigated
for two types of analytes, namely nanoscale objects (gold nanoparticles)
and molecules (11-mercaptoundecanoic acid). In the presence of the
pumping mechanism, a 4-fold increase in sensitivity was observed compared
to the purely photothermal effect, demonstrating the potential of
the presented photothermomechanical nanopumps for sensing applications
Photothermomechanical Nanopump: A Flow-Through Plasmonic Sensor at the Fiber Tip
Optical fibers equipped
with plasmonic flow sensors at their tips
are fabricated and investigated as photothermomechanical nanopumps
for the active transport of target analytes to the sensor surface.
The nanopumps are prepared using a bottom-up strategy: i.e., by sequentially
stacking a monolayer of a thermoresponsive polymer and a plasmonic
nanohole array on an optical fiber tip. The temperature-dependent
collapse and swelling of the polymer is used to create a flow-through
pumping mechanism. The heat required for pumping is generated by exploiting
the photothermal effect in the plasmonic nanohole array upon irradiation
with laser light (405 nm). Simultaneous detection of analytes by the
plasmonic sensor is achieved by monitoring changes in its optical
response at longer wavelengths (∼500–800 nm). Active
mass transport by pumping through the holes of the plasmonic nanohole
array is visualized by particle imaging velocimetry. Finally, the
performance of the photothermomechanical nanopumps is investigated
for two types of analytes, namely nanoscale objects (gold nanoparticles)
and molecules (11-mercaptoundecanoic acid). In the presence of the
pumping mechanism, a 4-fold increase in sensitivity was observed compared
to the purely photothermal effect, demonstrating the potential of
the presented photothermomechanical nanopumps for sensing applications
Photothermomechanical Nanopump: A Flow-Through Plasmonic Sensor at the Fiber Tip
Optical fibers equipped
with plasmonic flow sensors at their tips
are fabricated and investigated as photothermomechanical nanopumps
for the active transport of target analytes to the sensor surface.
The nanopumps are prepared using a bottom-up strategy: i.e., by sequentially
stacking a monolayer of a thermoresponsive polymer and a plasmonic
nanohole array on an optical fiber tip. The temperature-dependent
collapse and swelling of the polymer is used to create a flow-through
pumping mechanism. The heat required for pumping is generated by exploiting
the photothermal effect in the plasmonic nanohole array upon irradiation
with laser light (405 nm). Simultaneous detection of analytes by the
plasmonic sensor is achieved by monitoring changes in its optical
response at longer wavelengths (∼500–800 nm). Active
mass transport by pumping through the holes of the plasmonic nanohole
array is visualized by particle imaging velocimetry. Finally, the
performance of the photothermomechanical nanopumps is investigated
for two types of analytes, namely nanoscale objects (gold nanoparticles)
and molecules (11-mercaptoundecanoic acid). In the presence of the
pumping mechanism, a 4-fold increase in sensitivity was observed compared
to the purely photothermal effect, demonstrating the potential of
the presented photothermomechanical nanopumps for sensing applications
Photothermomechanical Nanopump: A Flow-Through Plasmonic Sensor at the Fiber Tip
Optical fibers equipped
with plasmonic flow sensors at their tips
are fabricated and investigated as photothermomechanical nanopumps
for the active transport of target analytes to the sensor surface.
The nanopumps are prepared using a bottom-up strategy: i.e., by sequentially
stacking a monolayer of a thermoresponsive polymer and a plasmonic
nanohole array on an optical fiber tip. The temperature-dependent
collapse and swelling of the polymer is used to create a flow-through
pumping mechanism. The heat required for pumping is generated by exploiting
the photothermal effect in the plasmonic nanohole array upon irradiation
with laser light (405 nm). Simultaneous detection of analytes by the
plasmonic sensor is achieved by monitoring changes in its optical
response at longer wavelengths (∼500–800 nm). Active
mass transport by pumping through the holes of the plasmonic nanohole
array is visualized by particle imaging velocimetry. Finally, the
performance of the photothermomechanical nanopumps is investigated
for two types of analytes, namely nanoscale objects (gold nanoparticles)
and molecules (11-mercaptoundecanoic acid). In the presence of the
pumping mechanism, a 4-fold increase in sensitivity was observed compared
to the purely photothermal effect, demonstrating the potential of
the presented photothermomechanical nanopumps for sensing applications
Photothermomechanical Nanopump: A Flow-Through Plasmonic Sensor at the Fiber Tip
Optical fibers equipped
with plasmonic flow sensors at their tips
are fabricated and investigated as photothermomechanical nanopumps
for the active transport of target analytes to the sensor surface.
The nanopumps are prepared using a bottom-up strategy: i.e., by sequentially
stacking a monolayer of a thermoresponsive polymer and a plasmonic
nanohole array on an optical fiber tip. The temperature-dependent
collapse and swelling of the polymer is used to create a flow-through
pumping mechanism. The heat required for pumping is generated by exploiting
the photothermal effect in the plasmonic nanohole array upon irradiation
with laser light (405 nm). Simultaneous detection of analytes by the
plasmonic sensor is achieved by monitoring changes in its optical
response at longer wavelengths (∼500–800 nm). Active
mass transport by pumping through the holes of the plasmonic nanohole
array is visualized by particle imaging velocimetry. Finally, the
performance of the photothermomechanical nanopumps is investigated
for two types of analytes, namely nanoscale objects (gold nanoparticles)
and molecules (11-mercaptoundecanoic acid). In the presence of the
pumping mechanism, a 4-fold increase in sensitivity was observed compared
to the purely photothermal effect, demonstrating the potential of
the presented photothermomechanical nanopumps for sensing applications