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Simoncelli S.,CONICET | Simoncelli S.,Institute Quimica Fisica Of Materiales | Aramendia P.F.,CONICET | Aramendia P.F.,University of Buenos Aires
Catalysis Science and Technology | Year: 2015

We explored the catalytic effect of 15 nm diameter gold nanoparticles (AuNPs) upon the thermal Z-E isomerization reaction of azobenzene and nine 4 and 4-4′ substituted azobenzenes (ABs). The kinetics follows a first order rate in ranges of [ABs] = 5 to 50 μM and [AuNPs] = 50 pM to 1 nM. A kinetic analysis of this compartmentalized system renders the thermal Z-E isomerization rate constant associated with each AuNP. Enhancements of 10- to 106-fold were measured for this rate constant in comparison to the same free ABs in solution. Experiments with selective Au facet coverage, as well as the kinetics studied in gold-silica core-shell nanoparticles (AuNP@SiO2) of different thicknesses, demonstrate the surface nature of the catalysis and allow one to evaluate the diffusion coefficient of azobenzene in the silica layer. This journal is © The Royal Society of Chemistry 2015.

Simoncelli S.,CONICET | Simoncelli S.,Institute Quimica Fisica Of Materiales | Roberti M.J.,CONICET | Roberti M.J.,Institute Quimica Fisica Of Materiales | And 4 more authors.
Journal of the American Chemical Society | Year: 2014

Single-molecule (SM) fluorescence microscopy was used to investigate the photochromic fluorescent system spiropyran-merocyanine (SP ↔ MC) interacting with gold nanoparticles (AuNPs). We observe a significant increase in the brightness of the emissive MC form, in the duration of its ON time, and in the total number of emitted photons. The spatial distribution of SMs with improved photophysical performance was obtained with 40 nm precision relative to the nearest AuNP. We demonstrate that even photochromic systems with poor photochemical performance for SM can become suitable for long time monitoring and high performance microscopy by interaction with metallic NP. © 2014 American Chemical Society.

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