11 research outputs found
Quantum Yield of Polariton Emission from Hybrid Light-Matter States
The efficiency of light-matter strong
coupling is tuned by precisely
varying the spatial position of a thin layer of cyanine dye J-aggregates
in FabryâPerot microcavities, and their photophysical properties
are determined. Placing the layer at the cavity field maximum affords
an interaction energy (Rabi splitting) of 503 meV, a 62% increase
over that observed if the aggregates are simply spread evenly through
the cavity, placing the system in the ultrastrong coupling regime.
The fluorescence quantum yield of the lowest polaritonic state Pâ
integrated over k-space is found to be âŒ10<sup>â2</sup>. The same value can be deduced from the 1.4 ps lifetime of Pâ
measured by femtosecond transient absorption spectroscopy and the
calculated radiative decay rate constant. Thus, the polariton decay
is dominated by nonradiative processes, in contrast with what might
be expected from the small effective mass of the polaritons. These
findings provide a deeper understanding of hybrid light-molecule states
and have implications for the modification of molecular and material
properties by strong coupling
Effets de l'ordonnance d'expropriation sur les baux ruraux
Important cellular events such as
division require drastic changes
in the shape of the membrane. These remodeling processes can be triggered
by the binding of specific proteins or by changes in membrane composition
and are linked to phospholipid metabolism for which dedicated enzymes,
named phospholipases, are responsible. Here wide-field fluorescence
microscopy is used to visualize shape changes induced by the action
of phospholipase A1 on dye-labeled supported membranes of POPC (1-palmitoyl-2-oleoly-<i>sn</i>-glycero-3-phosphocholine). Time-lapse imaging demonstrates
that layers either shrink and disappear or fold and collapse into
vesicles. These vesicles can undergo further transformations such
as budding, tubulation, and pearling within 5 min of formation. Using
dye-labeled phospholipases, we can monitor the presence of the enzyme
at specific positions on the membrane as the shape transformations
occur. Furthermore, incorporating the products of hydrolysis into
POPC membranes is shown to induce transformations similar to those
observed for enzyme action. The results suggest that phospholipase-mediated
hydrolysis plays an important role in membrane transformations by
altering the membrane composition, and a model is proposed for membrane
curvature based on the presence and shape of hydrolysis products
Quantum Strong Coupling with Protein Vibrational Modes
In
quantum electrodynamics, matter can be hybridized to confined
optical fields by a process known as lightâmatter strong coupling.
This gives rise to new hybrid lightâmatter states and energy
levels in the coupled material, leading to modified physical and chemical
properties. Here, we report for the first time the strong coupling
of vibrational modes of proteins with the vacuum field of a FabryâPerot
mid-infrared cavity. For two model systems, polyÂ(l-glutamic
acid) and bovine serum albumin, strong coupling is confirmed by the
anticrossing in the dispersion curve, the square root dependence on
the concentration, and a vacuum Rabi splitting that is larger than
the cavity and vibration line widths. These results demonstrate that
strong coupling can be applied to the study of proteins with many
possible applications including the elucidation of the role of vibrational
dynamics in enzyme catalysis and in H/D exchange experiments
Field-Controlled Charge Separation in a Conductive Matrix at the Single-Molecule Level: Toward Controlling Single-Molecule Fluorescence Intermittency
The
fluorescence intermittency or âblinkingâ of single
molecules of ATTO647N (ATTO) in the conductive matrix polyvinylcarbazole
(PVK) is described in the presence of an external applied electric
field. It is shown that due to the energy distribution of the highest
occupied molecular orbital (HOMO) level of PVK, which is energetically
close to the HOMO of ATTO, sporadic electron transfer occurs. As a
result, the on/off dynamics of blinking can be influenced by the electric
field. This field will, depending on the respective position and orientation
of the dye/polymer system with respect to those of the electrodes,
either enhance or suppress electron transfer from PVK to ATTO as well
as the back electron transfer from reduced ATTO to PVK. After the
charge-transfer step, the applied field will pull the hole in PVK
away from the dye, increasing the overall time the dye resides in
a dark state
Waveguide and Plasmonic Absorption-Induced Transparency
Absorption-induced
transparency (AIT) is one of the family of induced
transparencies that has emerged in recent decades in the fields of
plasmonics and metamaterials. It is a seemingly paradoxical phenomenon
in which transmission through nanoholes in gold and silver is dramatically
enhanced at wavelengths where a physisorbed dye layer absorbs strongly.
The origin of AIT remains controversial, with both experimental and
theoretical work pointing to either surface (plasmonic) or in-hole
(waveguide) mechanisms. Here, we resolve this controversy by carefully
filling nanoholes in a silver film with dielectric material before
depositing dye on the surface. Our experiments and modeling show that
not only do plasmonic and waveguide contributions to AIT both exist,
but they are spectrally identical, operating in concert when the dye
is both in the holes and on the surface
Ultrasensitive, Multiplex Raman Frequency Shift Immunoassay of Liver Cancer Biomarkers in Physiological Media
Highly sensitive multiplex biomarker
detection is critical for
the early diagnosis of liver cancer. Here, a surface-enhanced Raman
scattering (SERS) frequency-shift immunoassay is developed for detection
of liver cancer biomarkers α-fetoprotein and Glypican-3 down
to subpicomolar concentrations in saline solution. A high temperature
modification of the Tollenâs method affords silver nanoparticle
films with excellent SERS response upon which ordered domains of Raman
reporters are chemisorbed by microcontact printing. Shifts in the
reporters SERS spectrum in response to a bound antibodyâs biomarker
recognition constitutes the frequency shift assay, exhibiting here
exceptional sensitivity and specificity and shown to function in fetal
calf serum and in the serum of a patient with hepatocellular carcinoma
Surface Density-of-States Engineering of Anatase TiO<sub>2</sub> by Small Polyols for Enhanced Visible-Light Photocurrent Generation
Enhancement
of visible-light photocurrent generation by solâgel
anatase TiO<sub>2</sub> films was achieved by binding small polyol
molecules to the TiO<sub>2</sub> surface. Binding ethylene glycol
onto the surface, enhancement factors up to 2.8 were found in visible-light
photocurrent generation experiments. Density functional theory calculations
identified midgap energy states that emerge as a result of the binding
of a range of polyols to the TiO<sub>2</sub> surface. The presence
and energy of the midgap state is predicted to depend sensitively
on the structure of the polyol, correlating well with the photocurrent
generation results. Together, these results suggest a new, facile,
and cost-effective route to precise surface band gap engineering of
TiO<sub>2</sub> toward visible-light-induced photocatalysis and energy
storage
Electronic LightâMatter Strong Coupling in Nanofluidic FabryâPeÌrot Cavities
Electronic
lightâmatter strong coupling has been limited to solid molecular
films due to the challenge of preparing optical cavities with nanoscale
dimensions. Here we report a technique to fabricate such FabryâPeÌrot
nanocavities in which solutions can be introduced such that lightâmolecule
interactions can be studied at will in the liquid phase. We illustrate
the versatility of these cavities by studying the emission properties
of Chlorin e6 solutions in both the weak and strong coupling regimes
as a function of cavity detuning. Liquid nanocavities will broaden
the investigation of strong coupling to many solution-based molecular
processes
Vibro-Polaritonic IR Emission in the Strong Coupling Regime
The
strong coupling regime of lightâmatter interaction has
recently been extended to IR active molecular vibrations coupled to
microcavities, resulting in the formation of so-called vibro-polaritonic
states. Here we demonstrate the emissivity of such hybrid states.
Using thermal excitation, we achieve polaritonic IR emission from
a strongly coupled polymer. Thermal excitation of vibro-polaritons,
thus, constitutes an original way of establishing sizable excited-states
populations in strongly coupled systems and opens new routes to the
study of interacting vibro-polaritons
Coherent Coupling of WS<sub>2</sub> Monolayers with Metallic Photonic Nanostructures at Room Temperature
Room temperature strong coupling
of WS<sub>2</sub> monolayer exciton transitions to metallic FabryâPeÌrot
and plasmonic optical cavities is demonstrated. A Rabi splitting of
101 meV is observed for the FabryâPeÌrot cavity. The
enhanced magnitude and visibility of WS<sub>2</sub> monolayer strong
coupling is attributed to the larger absorption coefficient, the narrower
line width of the <i>A</i> exciton transition, and greater
spinâorbit coupling. For WS<sub>2</sub> coupled to plasmonic
arrays, the Rabi splitting still reaches 60 meV despite the less favorable
coupling conditions, and displays interesting photoluminescence features.
The unambiguous signature of WS<sub>2</sub> monolayer strong coupling
in easily fabricated metallic resonators at room temperature suggests
many possibilities for combining lightâmatter hybridization
with spin and valleytronics