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Subject: titanium dioxide × WGL Institute: INM ×

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    Crystallization behavior of poly(lactic acid)/titanium dioxide nanocomposites
    (Bangkok : King Mongkut’s University of Technology, 2015) Nomai, Jiraporn; Suksut, Buncha; Schlarb, Alois K
    In this study, a poly(lactic acid) (PLA) with various titanium dioxide (TiO2) nanoparticles loading were prepared by a manual laboratory mixing method. The effect of TiO2 nanoparticles on the non-isothermal and the isothermal crystallization behavior of PLA was investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The presence of TiO2 nanoparticles decreased the spherulite growth rate of PLA, whereas it initiated faster crystallization through the heterogeneous nucleation process as observed by optical microscopy. The results of DSC analyzes confirmed that the TiO2 nanoparticles act as an efficient nucleating agent for PLA crystallization. The cold crystallization temperature and crystallization half-time of PLA decreased, while the degree of crystallinity of PLA increased in relation to increases of TiO2 nanoparticles.
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    Ordered Mesoporous TiO2 Gyroids: Effects of Pore Architecture and Nb-Doping on Photocatalytic Hydrogen Evolution under UV and Visible Irradiation
    (Weinheim : Wiley-VCH, 2018) Dörr, Tobias Sebastian; Deilmann, Leonie; Haselmann, Greta; Cherevan, Alexey; Zhang, Peng; Blaha, Peter; de Oliveira, Peter William; Kraus, Tobias; Eder, Dominik
    Pure and Nb-doped TiO2 photocatalysts with highly ordered alternating gyroid architecture and well-controllable mesopore size of 15 nm via co-assembly of a poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) block copolymer are synthesized. A combined effort by electron microscopy, X-ray scattering, photoluminescence, X-ray photoelectron spectroscopy, Raman spectroscopy, and density functional theory simulations reveals that the addition of small amounts of Nb results in the substitution of Ti4+ with isolated Nb5+ species that introduces inter-bandgap states, while at high concentrations, Nb prefers to cluster forming shallow trap states within the conduction band minimum of TiO2. The gyroidal photocatalysts are remarkably active toward hydrogen evolution under UV and visible light due to the open 3D network, where large mesopores ensure efficient pore diffusion and high photon harvesting. The gyroids yield unprecedented high evolution rates beyond 1000 µmol h−1 (per 10 mg catalyst), outperforming even the benchmark P25-TiO2 more than fivefold. Under UV light, the Nb-doping reduces the activity due to the introduction of charge recombination centers, while the activity in the visible triple upon incorporation is owed to a more efficient absorption due to inter-bandgap states. This unique pore architecture may further offer hitherto undiscovered optical benefits to photocatalysis, related to chiral and metamaterial-like behavior, which will stimulate further studies focusing on novel light–matter interactions.