TiO2/PDMS nanocomposites for use on self-cleaning surfaces

AbstractIn this study, polydimethylsiloxane (PDMS)/TiO2 nanocomposite was processed by the spray method. TiO2 nanoparticles were synthesized by microwave-assisted hydrothermal method. Varying the proportion of nanoparticles in 0%, 0.5% and 1% by weight, commercial TiO2 (P25) was used for comparison purposes. The photocatalytic activity of nanocomposites impregnated with methylene blue was assessed by means of UV–visible spectroscopy. Changes in contact angle were analyzed before and after UV degradation tests. The effect of ultraviolet radiation on the chemical structure of the PDMS matrix was evaluated by Fourier transform infrared spectroscopy (FTIR). The results indicated that the addition of TiO2 nanoparticles in PDMS provides good photocatalytic properties in the decomposition of methylene blue, which is an important characteristic for the development of coatings for self-cleaning. For comparison purposes, commercial P25 was also used to investigate the photocatalytic activity

Composição florística e análise fitogeográfica de uma floresta semidecídua na Bahia, Brasil

The semideciduous forests of Bahia occur as highly fragmented areas and have only received a little attention from floristic and phytogeographical studies. These areas are mainly situated within the semi-arid region and isolated from the Coastal Atlantic Forest by the surrounding dry vegetation of the caatinga domain. This paper presents a floristic survey of a semideciduous forest fragment at Serra da Fazenda Retiro (SFR), Feira de Santana, Bahia State, in order to assess its phytogeographical relationships in comparison to caatinga vegetation and Atlantic Forest. The survey identified 173 species belonging to 143 genera and 59 families. Myrtaceae presented the highest species number (15 spp.), followed by Euphorbiaceae (13), Leguminosae (12), Malvaceae (7), Orchidaceae (7), and Rubiaceae (7). Additionally, three new species of the genera Neomarica (Iridaceae), Pseudobombax (Malvaceae), and Solanum (Solanaceae) were sampled. In spite of the studied area being located within the circumscription of the Caatinga Biome, analysis of similarity (UPGMA) and of the SFR species composition showed that it is more floristically related to semideciduous forest of the Atlantic Forest domain rather than to caatinga vegetation. © 2009 Instituto de Pesquisas Jardim Botanico do Rio de Janeiro. All Rights Reserved