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The studies probing the energy-transfer processes between water-soluble core/shell CdSe/ZnS quantum dots and many transition metal complexes are presented. The results have shown that the donor-acceptor interaction in solution is dominated by preassociation between the anionic CdSe/ZnS QDs and the cationic Cr(III) complexes prior to optical excitation.

The design, synthesis and characterization of cationic conjugated polyelectrolytes are described for determining the double-stranded DNA concentration [dsDNA]. The combination of the response from two different initial concentrations of conjugated polyelectrolytes has shown that it is possible to generate calibration curves that respond with a difference in [dsDNA] of over 7 orders of magnitude.

Two-photon excitation (TPE) is used to sensitize nitric oxide (NO) release from a dye-derivatized iron/sulfur/nitrosyl cluster Fe2(mu-RS)(sub 2)(NO)(sub 4) (Fluor-RSE, RS = 2-thioethyl ester of fluorescein) with near-infrared (NIR) light in the form of femtosecond pulses from a Ti:sapphire laser. The results show the potential utility of a two-photon antenna for sensitization of the photochemical release of an active agent from the photoactive pro-drug.

The two-step energy-transfer process in a self-assembled complex comprising a cationic conjugated polymer (CCP) and a dsDNA is investigated by using pump-dump-emission spectroscopy and time-correlated single-photon counting; energy is transferred from the CCP to an ethidium bromide (EB) molecule intercalated into the dsDNA through a fluorescein molecule linked to one terminus of the DNA. Time-dependent anisotropy measurements indicate that the inefficient direct energy transfer from the CCP to the intercalated EB results from the near orthogonality of their transition moments. These measurements also show that the transition moment of the fluorescein spans a range of angular distributions and lies between that of the CCP and EB. Consequently, the fluorescein acts as a fluorescence resonance energy-transfer gate to relay the excitation energy from the CCP to the EB. conjugated polymers | DNA sensors | time-resolved anisotrophy | ultrafast spectroscopy

The development and the mechanisms involved in one- and two-photon induced polymerization of methylmethacrylate using colloidal CdS semiconductor quantum dots (QDs) is presented. The efficiency of the photopolymerization process is shown to highly increase by the co-initiators.

The ability of the pulsed near-infrared light (NIR) absorbed by the hollow gold nanoshells (HGNs) to initiate the instantaneous release of the liposome contents is demonstrated. The approach has shown to be extremely useful in controlling the delivery of drugs to the selected disease sites with minimum toxicity.

The dye-derivatized iron sulfur nitrosyl cluster [Fe.sub.2][([mu]-RS).sub.2][(NO).sub.4] (AFX-RSE RS = 2-thioethyl ester of N-phenyl-N-(3-(2-ethoxy)phenyl)-7-(benzothiazol-2-yl)-9-9-diethyl-fluoren-2-ylamine) was prepared to investigate its single- and two-photon photochemistry and photophysics. Steady-state luminescence measurement have shown that AFX-RSE fluorescence is about 88% quenched relative to the model compound AF-tosyl, which is attributed to a relatively efficient energy transfer from the excited states of the antenna chromophores to the dinuclear metal center with the subsequent production of NO.

A series of organic- and water-soluble distyrylbenzene-based two-photon absorption (TPA) fluorophores containing dialkylamino donor groups at the termini is designed, synthesized and characterized. Results reveal a maximum TPA cross section (delta) in intermediate polarity solvent THF and was lowest in water.

The presence of micelles in aqueous media causes a large increase in the delta and etadelta of compounds the two-photon absorption fluorophores. The incorporation of the optically active units within the hydrophobic interior of the micelles is attributed by this enhancement.

A demonstration that nitric oxide (NO) can be photochemically generated through two-photon excitation (TPE) with 810 nm light of a suitable precursor in this case the supramolecular complex PPIX-RSE is presented. The TPE fluorescence data indicate that efficient energy transfer occurs from the porphyrin chromophore to the Fe2S2(NO)4 core resulting in fluorescence quenching and NO labilization.

A synthetic method, which can be used for the production of shape-adaptable water-soluble cationic conjugated polymers (CCPs) having a range of backbone regiochemistries, is presented. Results show that the Forster resonance energy transfer (FRET) efficiencies are improved because the polymers conform more tightly to the secondary structure of ds-deoxyribonucleic acid (DNA) and the findings could assist in improving the fluorescent DNA assays.

The synthesis of water-soluble TPA chromophores based on the [2.2]paracyclophane (pCp) core, which display exceptionally large eta delta values, is described. Each molecule can be considered to contain two distrylbenzene fragments held together by their internal rings through the pCp core and is expected to have a delta value approximately twice that of the constituent distrylbenzene chromophore.