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. PbCl₂ 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 PbI₂ 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