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The electronic and optical properties of S- and/or Ce-(co)doped anatase titanium dioxide (TiO2) are investigated using density functional theory plus U (DFTU) calculations. The optimized total energy suggests that TiO2 codoping by Ce and S favours the configuration of one substitutional Ce atom occupied on a Ti site with one substitutional S atom either on its nearest neighboring O or Ti site. The calculated results show that all doping configurations exhibit remarkable red-shift and excellent photocatalytic properties compared with pure TiO2. These reinforced features can mainly be ascribed to the appearance of S states in the top of valence band (VB) and Ce states in the bottom of conduction band (CB) as well as the contribution from the increasing octahedral dipole moments. The synergetic effects of cationic Ce and anionic S can extend optical absorption edge, which results in higher absorption coefficient in the visible light region than that of the anionic S monodoping and cationic Ce monodoping case; in the same time, decreasing the codoping concentration leads to reduced optical absorption. Additionally, Ce and S as cations incorporating into TiO2 lattices can induce stronger redox potential with a lower defect formation energy under O-rich condition compared with other doping systems. [ABSTRACT FROM AUTHOR]

A novel seven‐arm star block copolymer poly(L‐lactide‐star block‐N‐isopropylacrylamide) (PLLA‐sb‐PNIPAAm), comprised of a hydrophobic poly(L‐lactide) (PLLA) arm and an average of six hydrophilic poly(N‐isopropylacrylamide) (PNIPAAm) arms, was designed and synthesized. The amphiphilic PLLA‐sb‐PNIPAAm copolymer was capable of self‐assembling into nano‐sized micelle in water, which was confirmed by FT‐IR, 1H NMR and fluorescence spectroscopy. Transmission electron microscopy images showed that these nano‐sized micelles were regularly spherical in shape. Micelle size determined by size analysis was around 100 nm in diameter. The micelles showed reversible dispersion/aggregation in response to temperature changes through an outer polymer shell of PNIPAAm at around 31°C, observed by optical absorbance measurements. The anticancer drug methotrexate (MTX) as model drug was loaded in the polymeric nano‐sized micelles. In vitro release behavior of MTX was investigated, which showed a drastic thermoresponsive fast/slow switching behavior according to the temperature‐responsive structural changes of a micellar shell structure. The reversible and sensitive thermoresponse of this micelle might provide opportunities to construct a novel drug delivery system in conjunction with localized hyperthermia. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007 [ABSTRACT FROM AUTHOR]