8 research outputs found
DNA origami assembled nanoantennas for manipulating single-molecule spectral emission
Optical nanoantennas can affect the decay rates of nearby emitters by
modifying the local density of photonic states around them. In the
weak-coupling limit, and according to the Fermi's Golden Rule, the emission
spectrum of a dye is given by the energy of all the possible radiative
transitions weighted by the probability of each of them to occur. By
engineering the resonance of a nanoantenna, one can selectively enhance
specific vibronic transitions of a dye molecule, thus shaping its emission
spectrum. Since interactions between emitters and nanoantennas are known to be
position dependent, we make here use of DNA origami to precisely place an
individual dye at different positions around a gold nanorod. We show how this
relative position between the nanorod and the emitter affects the emission
spectrum of the latter. In particular, we observe the appearance of a second
fluorescence peak whose wavelength and intensity are correlated with the
fundamental plasmonic resonance of the nanorod, which we extract from its
photoluminescence spectrum. This second peak results from the selective
enhancement of transitions to different vibrational levels of the excitonic
ground state, whose energies are in resonance with the plasmonic one.
Furthermore, we argue that the drastic alteration of the fluorescence spectrum
in some of our samples cannot be accounted for with Kasha's rule, which
indicates that radiative and vibrational relaxation dye lifetimes can become
comparable through the coupling to the gold nanorods
Strong Plasmonic Enhancement of a Single PeridininâChlorophyll <i>a</i>âProtein Complex on DNA Origami-Based Optical Antennas
In
this contribution, we fabricate hybrid constructs based on a
natural light-harvesting complex, peridininâchlorophyll <i>a</i>âprotein, coupled to dimer optical antennas self-assembled
with the help of the DNA origami technique. This approach enables
controlled positioning of individual complexes at the hotspot of the
optical antennas based on large, colloidal gold and silver nanoparticles.
Our approach allows us to selectively excite the different pigments
present in the harvesting complex, reaching a fluorescence enhancement
of 500-fold. This work expands the range of self-assembled functional
hybrid constructs for harvesting sunlight and can be further developed
for other pigmentâproteins and proteins
Single-Molecule Positioning in Zeromode Waveguides by DNA Origami Nanoadapters
Nanotechnology is challenged by the
need to connect top-down produced
nanostructures with the bottom-up world of chemistry. A nanobiotechnological
prime example is the positioning of single polymerase molecules in
small holes in metal films, so-called zeromode waveguides (ZMWs),
which is required for single-molecule real-time DNA sequencing. In
this work, we present nanoadapters made of DNA (DNA origami) that
match the size of the holes so that exactly one nanoadapter fits in
each hole. By site-selective functionalization of the DNA origami
nanoadapters, we placed single dye molecules in the ZMWs, thus optimizing
the hole usage and improving the photophysical properties of dyes
compared to stochastically immobilized molecules
Broadband Fluorescence Enhancement with Self-Assembled Silver Nanoparticle Optical Antennas
Plasmonic
structures are known to affect the fluorescence properties
of dyes placed in close proximity. This effect has been exploited
in combination with single-molecule techniques for several applications
in the field of biosensing. Among these plasmonic structures, top-down
zero-mode waveguides stand out due to their broadband capabilities.
In contrast, optical antennas based on gold nanostructures exhibit
fluorescence enhancement on a narrow fraction of the visible spectrum
typically restricted to the red to near-infrared region. In this contribution,
we exploit the DNA origami technique to self-assemble optical antennas
based on large (80 nm) silver nanoparticles. We have studied the performance
of these antennas with far- and near-field simulations and characterized
them experimentally with single-molecule fluorescence measurements.
We demonstrate that silver-based optical antennas can yield a fluorescence
enhancement of more than 2 orders of magnitude throughout the visible
spectral range for high intrinsic quantum yield dyes. Additionally,
a comparison between the performance of gold and silver-based antennas
is included. The results indicate that silver-based antennas strongly
outperform their gold counterparts in the blue and green ranges and
exhibit marginal differences in the red range. These characteristics
render silver-based optical antennas ready for applications involving
several fluorescently labeled species across the visible spectrum
Gold Nanorod DNA Origami Antennas for 3 Orders of Magnitude Fluorescence Enhancement in NIR
DNA origami has taken a leading position in organizing
materials
at the nanoscale for various applications such as manipulation of
light by exploiting plasmonic nanoparticles. We here present the arrangement
of gold nanorods in a plasmonic nanoantenna dimer enabling up to 1600-fold
fluorescence enhancement of a conventional near-infrared (NIR) dye
positioned at the plasmonic hotspot between the nanorods. Transmission
electron microscopy, dark-field spectroscopy, and fluorescence analysis
together with numerical simulations give us insights on the heterogeneity
of the observed enhancement values. The size of our hotspot region
is âź12 nm, granted by using the recently introduced design
of NAnoantenna with Cleared HotSpot (NACHOS), which provides enough
space for placing of tailored bioassays. Additionally, the possibility
to synthesize nanoantennas in solution might allow for production
upscaling
DNA Origami Nanoantennas with over 5000-fold Fluorescence Enhancement and Single-Molecule Detection at 25 ÎźM
Optical nanoantennas are known to
focus freely propagating light and reversely to mediate the emission
of a light source located at the nanoantenna hotspot. These effects
were previously exploited for fluorescence enhancement and single-molecule
detection at elevated concentrations. We present a new generation
of self-assembled DNA origami based optical nanoantennas with improved
robustness, reduced interparticle distance, and optimized quantum-yield
improvement to achieve more than 5000-fold fluorescence enhancement
and single-molecule detection at 25 ÎźM background fluorophore
concentration. Besides outperforming lithographic optical antennas,
DNA origami nanoantennas are additionally capable of incorporating
single emitters or biomolecular assays at the antenna hotspot
Controlled Reduction of Photobleaching in DNA OrigamiâGold Nanoparticle Hybrids
The amount of information obtainable
from a fluorescence-based
measurement is limited by photobleaching: Irreversible photochemical
reactions either render the molecules nonfluorescent or shift their
absorption and/or emission spectra outside the working range. Photobleaching
is evidenced as a decrease of fluorescence intensity with time, or
in the case of single molecule measurements, as an abrupt, single-step
interruption of the fluorescence emission that determines the end
of the experiment. Reducing photobleaching is central for improving
fluorescence (functional) imaging, single molecule tracking, and fluorescence-based
biosensors and assays. In this single molecule study, we use DNA self-assembly
to produce hybrid nanostructures containing individual fluorophores
and gold nanoparticles at a controlled separation distance of 8.5
nm. By changing the nanoparticlesâ size we are able to systematically
increase the mean number of photons emitted by the fluorophores before
photobleaching
Placing Individual Molecules in the Center of Nanoapertures
While nanophotonic devices are unfolding
their potential for single-molecule
fluorescence studies, metallic quenching and steric hindrance, occurring
within these structures, raise the desire for site-specific immobilization
of the molecule of interest. Here, we refine the single-molecule cut-and-paste
technique by optical superresolution routines to immobilize single
fluorescent molecules in the center of nanoapertures. By comparing
their fluorescence lifetime and intensity to stochastically immobilized
fluorophores, we characterize the electrodynamic environment in these
nanoapertures and proof the nanometer precision of our loading method