Irradiation- and sensitizer-dependent changes in the lifetime of intracellular singlet oxygen produced in a photosensitized process.

Singlet oxygen, O(2)(a(1)Δ(g)), was produced upon pulsed-laser irradiation of an intracellular photosensitizer and detected by its 1275 nm O(2)(a(1)Δ(g)) → O(2)(X(3)Σ(g)(-)) phosphorescence in time-resolved experiments using (1) individual mammalian cells on the stage of a microscope and (2) suspensions of mammalian cells in a 1 cm cuvette. Data were recorded using hydrophilic and, independently, hydrophobic sensitizers. The microscope-based single cell results are consistent with a model in which the behavior of singlet oxygen reflects the environment in which it is produced; nevertheless, the data also indicate that a significant fraction of a given singlet oxygen population readily crosses barriers between phase-separated intracellular domains.

Photophysics of squaraine dyes: role of charge-transfer in singlet oxygen production and removal.

The unique optical properties of squaraines render these molecules useful for applications that range from xerography to photodynamic therapy. In this regard, squaraines derived from the condensation of nitrogen-based heterocycles and squaric acid have many promising attributes. Key solution-phase photophysical properties of six such squaraines have been characterized in this study.

Silica-coated gold nanorods with a gold overcoat: controlling optical properties by controlling the dimensions of a gold-silica-gold layered nanoparticle.

Silica shells were directly coated onto surfactant-capped gold nanorods by a simple one-step method. The procedure required no intermediate coating of the gold nanorod prior to the formation of the smooth silica shell, the thickness of which could be accurately controlled over the range 60-150 nm. These silica-encased gold nanorods were then covered with a gold overcoat to yield nanoparticles with unique optical properties that varied with the thicknesses of both the silica layer and the gold overcoat.

Influence of an intermolecular charge-transfer state on excited-state relaxation dynamics: solvent effect on the methylnaphthalene-oxygen system and its significance for singlet oxygen production.

The extent to which an intermolecular charge-transfer (CT) state can influence excited-state relaxation dynamics is examined for the system wherein 1-methylnaphthalene (MN) interacts with molecular oxygen. The MN-O2 system is ideally suited for such a study because excited states can be independently accessed by (i) irradiation into the discrete MN-O2 CT absorption band, (ii) direct irradiation of MN, and (iii) the photosensitized production of triplet state MN. Changing the solvent in which the MN-O2 system is dissolved influences the MN-dependent photoinduced production of singlet oxygen, O2(a1Delta(g)), which, in turn, yields information about fundamental concepts of state mixing.