Eyal Shafran

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Excitonic transitions in organic semiconductors are associated with large oscillator strength that limits the excited-state lifetime and can in turn impede long-range exciton migration. We present perylene-based emissive H-aggregate nanowires where the lowest energy state is only weakly coupled to the ground state, thus dramatically enhancing lifetime.(More)
The plasmonic resonances of nanostructured silver films produce exceptional surface enhancement, enabling reproducible single-molecule Raman scattering measurements. Supporting a broad range of plasmonic resonances, these disordered systems are difficult to investigate with conventional far-field spectroscopy. Here, we use nonlinear excitation spectroscopy(More)
Precision measurements of resonant energy transfer from isolated quantum dots (QDs) to individual carbon nanotubes (CNTs) exhibit unique features due to the one-dimensional nature of CNTs. In particular, excitons can be created at varying distances from the QD at different locations along the CNT length. This leads to large variations in energy transfer(More)
We demonstrate a near-field tomography method for investigating the coupling between a nanoscopic probe and a fluorescent sample. By correlating the arrival of single fluorescence photons with the lateral and vertical position of an oscillating tip, a complete three-dimensional analysis of the near-field coupling is achieved. The technique is used to reveal(More)
We demonstrate that the cycling between internal states of quantum dots during fluorescence blinking can be used to tune the near-field coupling with a sharp tip. In particular, the fluorescence emission from states with high quantum yield is quenched due to energy transfer, while that from low-yield states is elevated due to field enhancement. Thus, as a(More)
We apply scanning fluorescence correlation spectroscopy to study the structure of individual DNA coils in dilute and semidilute solutions. In dilute solutions, over two decades in length, from 0.6 to 46 μm, DNA behave as ideal chains, in agreement with theoretical predictions and in disagreement with prior experiments. In semidilute solutions, up to very(More)
We adapt a scanning fluorescence correlation spectroscopy technique to measure the structure factor of complex fluid systems and present the first measurements of the structure of semidilute solutions of long DNA polymers. The measured structure factors exhibit screening effects which, as expected for semidilute polymer solutions, grow stronger with(More)
Optical antennas can be used to manipulate the direction and polarization of radiation from an emitter. Usually, these metallic nanostructures utilize localized plasmon resonances to generate highly directional and strongly polarized emission, which is determined predominantly by the antenna geometry alone, and is thus not easily tuned. Here we show(More)
Temperature-dependent single-particle spectroscopy is used to study interfacial energy transfer in model light-harvesting CdSe/CdS core-shell tetrapod nanocrystals. Using alternating excitation energies, we identify two thermalized exciton states in single nanoparticles that are attributed to a strain-induced interfacial barrier. At cryogenic temperatures,(More)
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