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In this work, the synthesis and catalytic activity of bimetallic Ag–Au nanoparticles (NPs) supported in TiO2 mesoporous thin films (MTFs) are presented. The composite materials were obtained through a two-step procedure, performed at room conditions. In the first step, Ag NPs were grown inside the MTFs by photoreduction. Then, a galvanic replacement reaction with Au was carried out, yielding the bimetallic NPs. The composites were characterized by UV/Vis spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray reflectometry (XRR), which show that the alloyed Ag–Au NPs are present inside the mesopores. Moreover, Ag and Au composition relationship can be controlled by adjusting the reaction times of the photoreduction and galvanic replacement reactions, respectively. Pores remain accessible after NPs synthesis, a feature that ensures their possible applications in any device that requires the contact between the NPs and the medium. Catalytic activity of the composites towards 4-nitrophenol reduction by sodium borohydride was evaluated. Although all the bimetallic systems exhibit improved catalytic properties in comparison with the monometallic Ag composite, the sample with lower Au/Ag relationship is the most effective. For the first time, to the best of our knowledge, bimetallic Au–Ag NPs are encapsulated inside mesoporous TiO2 films, paving the way towards a wide variety of applications. Fil: Coneo Rodríguez, Rusbel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Dispositivos y Sensores; Argentina Fil: Moya, Sergio Eduardo. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Electrónica. Laboratorio de Instrumentación y Control; Argentina. CIC biomaGUNE; España Fil: Bruno, Mariano Martín. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina Fil: Angelome, Paula Cecilia. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentina

In this research work, DEXTRAN- and polyethyl- ene glycol (PEG)-coated iron-oxide superparamagnetic nano- particles were synthetized and their cytotoxicity and biodistribution assessed. Well-crystalline hydrophobic Fe3O4 SPIONs were formed by a thermal decomposition process with d 5 18 nm and r 5 2 nm; finally, the character of SPIONs was changed to hydrophilic by a post-synthesis pro- cedure with the functionalization of the SPIONs with PEG or DEXTRAN. The nanoparticles present high saturation mag- netization and superparamagnetic behavior at room tempera- ture, and the hydrodynamic diameters of DEXTRAN- and PEG-coated SPIONs were measured as 170 and 120 nm, respectively. PEG- and DEXTRAN-coated SPIONs have a Spe- cific Power Absorption SPA of 320 and 400 W/g, respectively, in an ac magnetic field with amplitude of 13 kA/m and fre- quency of 256 kHz. In vitro studies using VERO and MDCK cell lineages were performed to study the cytotoxicity and cell uptake of the SPIONs. For both cell lineages, PEG- and DEXTRAN-coated nanoparticles presented high cell viability for concentrations as high as 200 lg/mL. In vivo studies were conducted using BALB/c mice inoculating the SPIONs intrave- nously and exposing them to the presence of an external magnet located over the tumour. It was observed that the amount of PEG-coated SPIONs in the tumor increased by up to 160% when using the external permanent magnetic as opposed to those animals that were not exposed to the exter- nal magnetic field. V C

Advanced Functional Materials Vol. 17 (8), p. 1247 - 1254, Environment-sensitive Bragg reflectors are built using functional mesoporous thin films as building blocks. Tuning of optical properties is achieved by changing the composition or porosity of the slabs or the introduction of planar defects. Sorption or capillary condensation of molecules into the pore system results in a 10-40 nm photonic bandgap (PBG) shift. Organic functions added to the pore surface change the response, permitting tailoring of the selectivity towards small-size molecules.

A study of the case of superlattices of Au nanoparticles passivated with thiol molecules is presented. The possibility of an orientation relationship among the nanoparticles is analyzed. It is concluded that for the case of Au the relationship does not exist. In-situ experiments in the TEM showing loss of order and the melting conditions are reported and discussed. Different temperature ranges are clearly distinguished for the loss of the thiol-thiol bonds and for the Au nanoparticles-thiol bonds.