Photochemical strategies for the seed-mediated growth of gold and gold-silver nanoparticles.

Gold nanoparticles (AuNP) can be used as seeds for the synthesis of larger AuNP of controllable size with narrow size distribution by photochemical reduction of additional Au(III) using water-soluble benzoins or H(2)O(2) as sources of reducing radicals. Further, beyond simply enlarging the AuNP, it is possible to add a shell of another metal, such as silver, leading to Au/Ag core-shell structures with controllable dimensions for both core and shell. This strategy illustrates the fine spatial and temporal control achievable using clean photochemical techniques without the addition of hard surface ligands often necessary to control the size and structure of gold-silver nanostructures.

Opportunistic use of tetrachloroaurate photolysis in the generation of reductive species for the production of gold nanostructures.

The photolysis of gold salts is rarely viewed as the initiation for gold nanoparticle (AuNP) formation. Yet, photolysis of AuCl(4)(-) generates chlorine atoms whose rich hydrogen transfer chemistry can readily generate strongly reducing radicals. Interesting precursors include hydrogen peroxide, 2-propanol, 1,4-cyclohexadiene and tetrahydrofuran; all of them yield strongly reducing radicals.

Surface plasmons control the dynamics of excited triplet states in the presence of gold nanoparticles.

Aqueous gold nanoparticles (AuNPs) cause a large increase in the yield of methylene blue triplets ((3)MB*) obtained upon 650 nm laser excitation as a result of surface plasmon field interactions that can be described as transmitter-receiver antenna effects. Two distinct (3)MB* populations are observed; a fast decaying one (tau(T) approximately 25 ns) is believed to be due to molecules on the AuNP surface at the time of excitation and is described as static quenching. A longer lived (3)MB* population has lifetimes in the tens of microseconds but is subject to an anomalously high rate constant for a AuNP quenching of 6.

Synthesis of copper nanoparticles mediated by photogenerated free radicals: catalytic role of chloride anions.

The photodecomposition of ketones by the Norrish Type I reaction, leading to the efficient release of reducing ketyl or alpha-amino alkyl radicals, provides a facile route for the synthesis of copper nanoparticles (CuNP) in both aqueous and organic solvents. The role of different counterions (especially halides) and surfactants has been used to 'tune' the morphology and size of the nanostructures formed. In aqueous solutions chloride ions catalyze the disproportionation that mediates the Cu(I) --> Cu(0) --> CuNP conversion.

Photochemical strategies for the synthesis of gold nanoparticles from Au(III) and Au(I) using photoinduced free radical generation.

A comprehensive study of the ketone-photoinduced formation of gold nanoparticles (AuNPs) from gold ions in aqueous and micellar solution has been carried out. Ketones are good photosensitizers for nanoparticle synthesis not because of the energy they can absorb or deliver but rather because of the reducing free radicals they can generate; thus, efficient nanoparticle generation requires a careful selection of substrates and experimental conditions to ensure that free-radical generation occurs with high quantum efficiency and that gold ion precursors do not cause UV screening of the organic photosensitizers. A key consideration in achieving AuNP synthesis with short exposure times is minimizing excited-state quenching by gold ions; this can be achieved by temporal or spatial segregation or a combination of the two.

Facile photochemical synthesis of unprotected aqueous gold nanoparticles.

Aqueous, unprotected gold nanoparticles were prepared from HAuCl4 using a water-soluble benzoin (Irgacure-2959) as a photochemical source of strongly reducing ketyl radicals. This rapid method provides spatiotemporal control of nanoparticle generation, while light intensity can be used to control particle size. The particles are stable for months and do not require any of the conventional (S, N, or P) stabilizing ligands, although these can be readily incorporated if required.

A simple and smart oxygen sensor based on the intrazeolite reactions of a substituted anthraquinone.

Inclusion of 2-(hydroxymethyl)anthraquinone in zeolite NaY leads to a solid, photoactivated, reusable oxygen sensor capable of reporting and memorizing oxygen contamination events by simple visual inspection.