Learn More
Photoluminescence blinking--random switching between states of high (ON) and low (OFF) emissivities--is a universal property of molecular emitters found in dyes, polymers, biological molecules and artificial nanostructures such as nanocrystal quantum dots, carbon nanotubes and nanowires. For the past 15 years, colloidal nanocrystals have been used as a(More)
Generation of multiple electron-hole pairs (excitons) by single photons, known as carrier multiplication (CM), has the potential to appreciably improve the performance of solar photovoltaics. In semiconductor nanocrystals, this effect usually has been detected using a distinct dynamical signature of multiexcitons associated with their fast Auger(More)
Four new helical oligoproline assemblies containing 16, 17, 18, and 19 proline residues and ordered arrays of a Ru(II)-bipyridyl chromophore and a phenothiazine electron-transfer donor have been synthesized in a modular fashion by solid-phase peptide synthesis. These arrays are illustrated and abbreviated as(More)
The performance of photovoltaic and photochemical devices is directly linked to the efficiency with which absorbed photons are converted into electron-hole pairs (excitons). A usual assumption is that one photon produces a single exciton, while the photon energy in the excess of the material's energy gap (the gap that separates the conduction from the(More)
We study ultrafast photoluminescence (PL) dynamics of Si nanocrystals (NCs). The early-time PL spectra (<1 ns), which show strong dependence on NC size, are attributed to emission involving NC quantized states. The PL spectra recorded for long delays (>10 ns) are almost independent of NC size and are likely due to surface-related recombination. Based on(More)
Resonance Raman spectroscopy is applied to the cyanide adducts of cytochrome P450cam and its T252A and D251N site-directed mutants, both in their substrate-free and camphor-bound forms, to probe active-site heme structure and, in particular, interactions of the FeCN fragment with potential active-site H-bond donors. In contrast to the ferrous CO and ferric(More)
Resonance Raman spectroscopy has been used to investigate the properties of cyanide-bound beef liver catalase (BLC) and Aspergillus niger catalase (ANC) in the pH range 4.9-11.5. Evidence has been obtained for the binding of cyanide to both BLC and ANC in two binding geometries. The first conformer, exhibiting the nu[Fe-CN] stretching mode at a higher(More)
Effects of air exposure on surface properties, electronic structure, and carrier relaxation dynamics in colloidal PbSe nanocrystals (NCs) were studied using X-ray photoelectron spectroscopy, transmission electron microscopy, and steady-state and time-resolved photoluminescence (PL) spectroscopies. We show that exposure of NC hexane solutions to air under(More)
A molecular assembly based on derivatized polystyrene is described, which mimics both the light-harvesting and energy-conversion steps of photosynthesis. The system is unique in that the two key parts of a photosynthetic system are incorporated in a functional assembly constructed from polypyridine complexes of Ru(II). This system is truly artificial, as(More)
We demonstrate novel methods for the study of multiple exciton generation from a single photon absorption event (carrier multiplication) in semiconductor nanocrystals (or nanocrystal quantum dots) that are complementary to our previously reported transient absorption method. By monitoring the time dependence of photoluminescence (PL) from CdSe nanocrystals(More)