1,721,030 research outputs found
Editorial: Application of Photocatalysts in Environmental Chemistry
Full text linkThe removal of contaminants from wastewater, which are produced by human activities, and the development of new means of renewable energy production are the main issues that need to be addressed to solve environmental problems [...
Multifunctional TiO2/FexOy/Ag based nanocrystalline heterostructures for photocatalytic degradation of a recalcitrant pollutant
No full textThe photocatalytic degradation of pollutants is a key technological application for nanomaterials. Our work aims at developing a multifunctional nanocrystalline heterostructure based on TiO2nanorods, FexOyand Ag nanoparticles (NPs), TiO2NRs/FexOy/Ag, integrating in one nanostructure a visible light photoactive moiety (TiO2NRs/Ag) and a magnetic domain (FexOy), in order to address the photoactivity under visible light and the possibility of recovery and reuse the photocatalyst. The synthesis was carried by preparing first the TiO2NRs/FexOybased heterostructure and then growing Ag NPs with control on size. The resulting multidomain structures were characterized by FTIR and absorption spectroscopy, TEM and SEM microscopy, EDS and XRD analysis. The influence of the Ag NP domain and of its size on the photoactivity of the TiO2NRs/FexOy/Ag nanostructures under visible light were investigated in the photocatalytic degradation of the Nalidixic Acid, an antibiotic used as a model compound representative of recalcitrant pollutants. In the presence of the Ag domain a significant increase of the photoactivity with respect to TiO2NRs/FexOyheterostructures and to the commercially available TiO2P25 was observed. Such an enhanced photocatalytic efficiency was found dependent on the size of the Ag domain and explained taking into account the plasmonic properties and the different possible photoactivation mechanisms
Patterned assembly of luminescent nanocrystals: Role of the molecular chemistry at the interface
No full textA simple fabrication approach for achieving nanoparticle patterns based on a room temperature chemically driven strategy is reported. Suitably engineered colloidal luminescent nanocrystals (NCs) (4 and 6 nm in diameter), namely organic capped and silica-coated negatively charged CdSe@ZnS NCs, have been selectively assembled onto defined domains in a binary hydrophobic/hydrophilic chemical pattern, purposely fabricated by combining microcontact printing and wet chemistry procedures. The goal of the work has been to investigate the experimental parameters governing the assembly process at molecular level, in order to elucidate factors regulating interactions at the interfaces. For this purpose, specific sets of conditions, namely substrate patterns and NCs with distinct surface functionalization, have been prepared and tested using different NC dispersing solvents. The NC assembly has been demonstrated driven by non-covalent forces, namely Van der Waals or electrostatic interactions occurring at the NC/substrate interface. The overall study has provided a comprehensive understanding of the role of solvent and molecular chemistry at interfaces in NC assembling. The obtained results can be valuable to set up reliable procedures for developing reproducible patterning protocols potentially useful for the fabrication of NC-based devices. © 2014 Springer Science+Business Media
Photocatalytic Synthesis of Silver Nanoparticles Stabilized by TiO2 Nanorods: A Semiconductor/Metal Nanocomposite in Homogeneous Nonpolar Solution
No full textAbstract: A novel colloidal approach toward semiconductor/metal nanocomposites is presented. Organicsoluble anatase TiO2 nanorods are used for the first time to stabilize Ag nanoparticles in optically clear nonpolar solutions in the absence of specific ligands for silver. Metallic silver is generated upon UV illumination of deaerated TiO2 solutions containing AgNO3. The Ag nanoparticles can be obtained in different size-morphological regimes as a function of the irradiation time, due to light-induced phototragmentation and ripening processes. A mechanism for the colloidal stabilization of the silver nanoparticles is tentatively suggested, which regards the TiO2 nanorods as inorganic stabilizers, thus acting in the same manner as conventional surfactant molecules. The proposed photocatalytic approach offers a convenient method for producing TiO2/Ag nanocomposite systems with a certain control over the metal particle size without the use of surfactants and/or additives. Stable colloidal TiO2-nanorod-stabilized Ag nanoparticles can be potentially available for a number of applications that require "clean" metal surfaces, such as homogeneous organic catalysis, photocatalysis, and sensing devices
Role of Metal Nanoparticles in TiO2/Ag Nanocomposite-Based Microheterogeneous Photocatalysis
No full textThe photocatalytic performance of anatase TiO2 nanorod-stabilized Ag nanoparticles has been investigated during the reductive bleaching of a model dye, Uniblue A (UBA), in homogeneous organic solutions. The activity of the TiO2/Ag nanocomposite has been found to vary continuously during the course of photocatalysis, following a concomitant light-induced modification of the metal nanoparticle size and size distribution. The direct involvement of the metal particles in mediating electron transfer between photoexcited TiO2 and the target UBA is explained on the basis of the size-dependent redox properties of the metal nanoparticles. The present results can be useful in the design of new composite materials with well-tailored photocatalytic properties and long-term stability
Plasmonic photoheating of gold nanorods in thermo-responsive chiral liquid crystals
No full textWe report on the thermo-optical properties of gold nanorods (GNRs) dispersed in a thermotropic cholesteric liquid crystal (CLC). We have characterized the CLC reflection band behavior for two different cell thicknesses under the influence of a suitable (resonant) pump beam. It turns out that for the 1.6 μm thick cell there is a suppression of the CLC reflection band for both pure CLC and CLC/GNRs. For the 10 μm thick cell, the presence of GNRs desensitizes the shift of the CLC reflection band to temperature. Suitable cell design enables one to 'turn off' the wavelength shift of the peak reflection, thereby turning the system into a pure amplitude measurement tool. This has implications where the probe wavelength is fixed at a common, single wavelength
Luminescent nanocrystals in phospholipid micelles for bioconjugation: An optical and structural investigation
No full textOrganic capped luminescent CdSe@ZnS nanocrystals (NCs) have been incorporated in block copolymer micelles, formed by polyethylene glycol modified phospholipids (PEG lipids). The obtained water soluble NC including PEG lipid micelles have been conjugated with bovine serum albumine (BSA). The entire process has been investigated by using optical, structural and electrophoretic complementary techniques. Such an integrated approach has allowed to elucidate critical issues, such as the time and temperature effects on the phase behavior of the PEG lipid/NC aggregate structures, the emitting properties of the NCs before and after micelle formation and bio-conjugation and the effect of conjugation on the biological moiety. The overall results provide relevant insight on the fabrication of the bio-conjugates, on their stability and on preparative procedure reproducibility, in view of the use of the resulting protein decorated NCs as multifunctional hybrid building blocks for the fabrication of a variety of supramolecular assemblies to exploit in biological sensing and diagnostic applications
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