Search results for "Single Molecule Spectroscopy"

Chapter 2 Single molecule spectroscopy of multichromophoric dendrimers at room and liquid helium temperatures

2004

Publisher Summary This chapter discusses the single molecule spectroscopy of multichromophoric dendrimers at room and liquid helium temperatures. Single molecule spectroscopy has become an important tool for the optical study of the electronic interactions of proximate chromophores as the electronic interactions can be studied without averaging over the properties of an intrinsically heterogeneous ensemble. Single perylenemonoimide (PMI) chromophores are selectively addressed in the frequency domain within spatially isolated multichromophoric dendrimers, which are dispersed in a polymer film. Although the chromophores are interacting, they still can be addressed separately. This feature in …

Fluorescence and spin properties of defects in single digit nanodiamonds

2009

International audience; This article reports stable photoluminescence and high-contrast optically detected electron spin resonance (ODESR) from single nitrogen-vacancy (NV) defect centers created within ultrasmall, disperse nanodiamonds of radius less than 4 nm. Unexpectedly, the efficiency for the production of NV fluorescent defects by electron irradiation is found to be independent of the size of the nanocrystals. Fluorescence lifetime imaging shows lifetimes with a mean value of around 17 ns, only slightly longer than the bulk value of the defects. After proper surface cleaning, the dephasing times of the electron spin resonance in the nanocrystals approach values of some microseconds, …

Investigation of molecular dimers by ensemble and single molecule spectroscopy

2002

International audience; We have investigated molecular dimers with different electronic coupling strengths by bulk and single molecule spectroscopy. In one of the dimers the two monomers (perylene-monoimide) are directly connected via a single bond while in the other one they are separated by the benzil motif. The close proximity of the monomers in the first case gives rise to excitonic band splitting which is clearly observable in the bulk absorption spectra. For the benzil structure the electronic interactions are governed by Förster-type energy hopping between the monomers. Fluorescence intensity trajectories at the single molecule level show one-step and two-step bleaching behaviour whi…

Single Molecule Spectroscopy of Oriented Recombinant Trimeric Light Harvesting Complexes of Higher Plants

2002

The bleaching dynamics of reconstituted single light-harvesting chlorophyll a/b investigated. The complexes containing one histidine6 tag per monomeric subunit were immobilised predominantly in a defined orientation with their symmetry axis perpendicular to a Ni-ion-containing surface allowing for the first time the examination of single LHCIIb in an aqueous environment. Most complexes exhibit photobleaching in one step, indicating coupling between the monomeric subunits leading to an energy transfer between adjacent subunits. Differences in bleaching behaviour between these and previous observations with single LHCIIb are discussed.

Watching the photo-oxidation of a single aromatic hydrocarbon molecule

2001

International audience; The photooxidation of single dye molecules (see scheme) can be followed by confocal fluorescence microscopy. The self-sensitized reaction with singlet oxygen leads to a suite of products, which may be differentiated spectrally. Tentative structures for certain photoproducts have been obtained from quantum-chemical calculations.

Single Molecule Spectroscopy: Methodological Developments and Experiments at Low Temperature

2001