5 research outputs found
Dissecting Hidden Couplings Using Fifth-Order Three-Dimensional Electronic Spectroscopy
We report the demonstration of single-quantum 3D electronic spectroscopy. Utilizing the recently introduced gradient assisted photon echo (GRAPE) methodology, the fifth-order nonlinear polarization of the solvatochromatic dye IR144 corresponding to evolution through three sequential single-quantum coherences is measured. GRAPE, which allows a 2D slice of data to be acquired in parallel, permits a practical implementation of 3D spectroscopy at optical frequencies in a matter of minutes instead of hours. By spreading frequencies into a third spectral dimension, we can resolve features in the spectra that are otherwise obscured. For IR144, a previously unresolved cross peak originating from high frequency vibronic modes is observed in the spectrum. Theoretical modeling based on the cumulant expansion truncated at second order reproduces the main features of the experimental results. This experimental approach will enable further high dimensional spectroscopic experiments
Correction to “Energy Transfer Observed in Live Cells Using Two-Dimensional Electronic Spectroscopy”
Correction
to “Energy Transfer Observed in
Live Cells Using Two-Dimensional Electronic Spectroscopy
Energy Transfer Observed in Live Cells Using Two-Dimensional Electronic Spectroscopy
Two-dimensional
electronic spectroscopy (2DES) elucidates electronic
structure and dynamics on a femtosecond time scale and has proven
to be an incisive tool for probing congested linear spectra of biological
systems. However, samples that scatter light intensely frustrate 2DES
analysis, necessitating the use of isolated protein chromophore complexes
when studying photosynthetic energy transfer processes. We present
a method for conducting 2DES experiments that takes only seconds to
acquire thousands of 2DES spectra and permits analysis of highly scattering
samples, specifically whole cells of the purple bacterium Rhodobacter sphaeroides. These in vivo 2DES experiments
reveal similar time scales for energy transfer within the antennae
complex (light harvesting complex 2, LH2) both in the native photosynthetic
membrane environment and in isolated detergent micelles
Thickness-Controlled Quasi-Two-Dimensional Colloidal PbSe Nanoplatelets
We
demonstrate controlled synthesis of discrete two-dimensional
(2D) PbSe nanoplatelets (NPLs), with measurable photoluminescence,
via oriented attachment directed by quantum dot (QD) surface chemistry.
Halide passivation is critical to the growth of these (100) face-dominated
NPLs, as corroborated by density functional theory studies. PbCl<sub>2</sub> moieties attached to the (111) and (110) of small nanocrystals
form interparticle bridges, aligning the QDs and leading to attachment.
We find that a 2D bridging network is energetically favored over a
3D network, driving the formation of NPLs. Although PbI<sub>2</sub> does not support bridging, its presence destabilizes the large (100)
faces of NPLs, providing means for tuning NPL thickness. Spectroscopic
analysis confirms the predicted role of thickness-dependent quantum
confinement on the NPL band gap
Shape-Controlled Narrow-Gap SnTe Nanostructures: From Nanocubes to Nanorods and Nanowires
The rational design and synthesis
of narrow-gap colloidal semiconductor
nanocrystals (NCs) is an important step toward the next generation
of solution-processable photovoltaics, photodetectors,
and thermoelectric devices. SnTe NCs are particularly attractive
as a Pb-free alternative to NCs of narrow-gap lead chalcogenides.
Previous synthetic efforts on SnTe NCs have focused on spherical nanoparticles.
Here we report new strategies for synthesis of SnTe NCs with shapes
tunable from highly monodisperse nanocubes, to nanorods
(NRs) with variable aspect ratios, and finally to long, straight nanowires
(NWs). Reaction at high temperature quickly forms thermodynamically
favored nanocubes, but low temperatures lead to elongated particles.
Transmission electron microscopy studies of reaction products at various
stages of the synthesis reveal that the growth and shape-focusing
of monodisperse SnTe nanocubes likely involves interparticle
ripening, while directional growth of NRs and NWs may be initiated
by particle dimerization via oriented attachment