RESUMO
Exploiting the intrinsic photosensitivity of TiO2 nanoparticles, we demonstrated how ultraviolet (UV) pulsed laser irradiation of acrylate polymer nanocomposite solutions can separate the initial clusters of these colloidal semiconductor nanorods into clearly distinct units. From the irradiated solutions, optically clear nanocomposite films are obtained which exhibit enhanced optical properties with respect to the nanocomposites obtained without previous UV treatment.
RESUMO
A simple and versatile light-based strategy to grow low-dimensional gold superstructures is presented; prolonged UV-irradiation of TiO2 nanorod-stabilized Au nanoparticles in organic media promotes the progressive formation of distinctive chainlike metal assemblies, namely segments of a few gold particles, 2D or quasi-1D large structures composed of interlacing lines of hundreds of metal units over areas of about 500 nm2.
Assuntos
Ouro/química , Nanopartículas/química , Nanotubos/química , Titânio/química , Nanotubos/efeitos da radiação , Tamanho da Partícula , Propriedades de Superfície , Titânio/efeitos da radiação , Raios UltravioletaRESUMO
Hetero-structures formed by quantum-sized ZnO nanocrystals and photosynthetic pigments were prepared by adsorbing either chlorophyll a, carotenoids or their mixture onto a film of organic-capped ZnO nanoparticles. Photoelectrochemical measurements were comparatively performed on both bulk and nanocrystalline ZnO films after dye-covering in order to probe the photosensitization process occurring at the hetero-junction. The photoconversion process was found to be greatly enhanced at the nanocrystalline electrodes upon sensitization with a dye mixture. The sensitization process is discussed on the basis of the aggregation state of chlorophyll a, and of the specific photoprotective action played by carotenoids.
Assuntos
Cristalização/métodos , Nanotubos/química , Nanotubos/ultraestrutura , Complexo de Proteínas do Centro de Reação Fotossintética/química , Complexo de Proteínas do Centro de Reação Fotossintética/efeitos da radiação , Óxido de Zinco/química , Carotenoides/química , Carotenoides/efeitos da radiação , Clorofila/química , Clorofila/efeitos da radiação , Clorofila A , Materiais Revestidos Biocompatíveis/química , Materiais Revestidos Biocompatíveis/efeitos da radiação , Fontes de Energia Elétrica , Eletroquímica/métodos , Eletrodos , Luz , Nanotubos/efeitos da radiação , Tamanho da Partícula , Fotoquímica/métodosRESUMO
In this work, we report on the degradation of methyl-red (2-(4-Dimethylamino-phenylazo)-benzoic acid--C.I. 13020) under UV irradiation in the presence of nanosized ZnO and TiO2. Oxide nanocrystals with controlled size were synthesised by using non-hydrolytic approaches and tested for the photocatalysed degradation. The performances of the immobilised nanoparticles were compared with their commercial counterparts after immobilization onto a solid support. The influence of some experimental conditions, namely pH and dye concentration, were investigated by monitoring the dye decoloration spectrophotometrically. Several intermediate by-products were identified by HPLC-MS, showing that two different mechanisms were operative during the photocatalytic oxidation.