Polytechnic University of Valencia

About: Polytechnic University of Valencia is a education organization based out in Valencia, Spain. It is known for research contribution in the topics: Catalysis & Population. The organization has 16282 authors who have published 40162 publications receiving 850234 citations.

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

Abstract: 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. Temporal segregation can be accomplished by using unimolecular precursors, such as benzoins, that yield ketyl radicals from triplet precursors with lifetimes of a few nanoseconds. Spatial segreg...

New advances in fluorogenic anion chemosensors.

Abstract: The development of anion chemosensors is an area of recent interest. We make here a comprehensive review of new advances on anion chemosensing, reported in the literature during the year 2004. The review follows a classification of the sensing systems based on design principles. It comprises: the binding site-signalling subunit approach, the displacement approach and the use of fluoro-chemodosimeters. The first two approximations are based on the use of a suitable anion coordination site coupled with a signalling unit which signals the anion coordination process via changes in its fluorescence behaviour. The two basic subunits are covalently linked in the binding site-signalling subunit approach and not in the displacement approach. In both approaches the fluorescence variation is reversible. The third way to the development of fluorogenic chemosensors is the use of chemodosimeters (also called reagents or reactands) that work usually through irreversible chemical reactions coupled with drastic changes in the fluorescence emission behaviour.

A Colorimetric ATP Sensor Based on 1,3,5-Triarylpent-2-en-1,5-diones

Abstract: A new family of chromogenic ionophores for anion sensing has been developed with 1,3,5-triarylpent-2-en-1,5-diones. These species form yellow solutions that undergo a color change to magenta in the presence of certain inorganic ions or nucleotides, depending on the derivative. The reaction with ATP is particulary remarkable and therefore these compounds are chromogenic reagents for "naked-eye" sensing of ATP. The picture shows the color changes induced on one derivative in the presence of GMP, ADP, and ATP (from left to right).

Dispersive phonon linewidths: the E2 phonons of ZnO.

Abstract: Phonon linewidths can exhibit a large variation when either pressure or isotopic masses are changed. These effects yield detailed information about the mechanisms responsible for linewidths and lifetimes, e.g., anharmonicity or isotopic disorder. We report Raman measurements of the linewidth of the upper ${\mathrm{E}}_{2}$ phonons of ZnO crystals with several isotopic compositions and their dependence on pressure. Changes by a factor of 12 are observed at a given temperature. Comparison with calculated densities of one-phonon states, responsible for isotope scattering, and of two-phonon states, responsible for anharmonic decay, yields a consistent picture of these phenomena. Isotopic disorder broadening by $7\text{ }\text{ }{\mathrm{c}\mathrm{m}}^{\ensuremath{-}1}$ is found in samples with mixed $^{16}\mathrm{O}--^{18}\mathrm{O}$ content, whereas the anharmonic processes involve decay into sums and differences of two phonons.