Lanthanum phenylphosphonate (LaHPP) was synthesized through solution reflux method with a hydrothermal reaction. The synergistic effect of decabromodiphenyl oxide (DBDPO) and LaHPP on thermal stability and flame retardancy of polycarbonate (PC) were investigated. Transmission electron microscope graphs showed that LaHPP dispersed well in the PC matrix. Thermogravimetric analyses indicated that the addition of LaHPP into PC/DBDPO composites led to better thermal stability. An appropriate content (1 wt%) of LaHPP could improve the UL94 rating (from V-2 to V-0) and limiting oxygen index value (from 32.8 to 40.5%) dramatically, and also brought an effective reduction in peak heat release rate and smoke release rate in cone calorimeter. Investigation of gaseous pyrolysis products and char residues demonstrated that LaHPP promoted the formation of more compact and solid chars, which acted as physical barriers to inhibit heat and oxygen transfer. The inside char layers also provided more space and time for DBDPO to play its flame retardant role in gaseous phases. POLYM.

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TiO 2 photocatalysts co-doped with N and Fe were synthesized by the sol-gel method. Cooperation of N and Fe in the co-doped TiO 2 was studied by monitoring NH 3 decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis) absorption spectroscopy, and simulation based on density functional theory (DFT). The results from NH 3 decomposition revealed that cooperation of N and Fe broadened the range of response of TiO 2 to visible light and also enhanced the photocatalytic activity of TiO 2 under ultraviolet light. The XRD patterns and SEM and HRTEM images indicated that the co-doped samples prepared were nanometric anatase with an average particle size of 20 nm. Co-doping with N and Fe inhibited grain growth of TiO 2 and resulted in larger lattice distortion. XPS analysis showed that the doped N and Fe atoms were replacing lattice oxygen and Ti atoms, respectively. UV-Vis absorption spectra of the co-doped sample showed that the optical absorption edge had been shifted to approximately 675 nm. The DFT results confirmed that cooperation of the Fe3d and N2p orbits reduced the energy gap of TiO 2 and thus broadened its range of response to visible light. The synergistic action of the electron density around N and Fe in the co-doped TiO 2 enhanced its photochemical stability. In addition, a photocatalytic reaction mechanism for TiO 2 co-doped with N and Fe revealed the presence of N2p, Fe3d, and Ti3d orbits as photogenerated holeelectron traps, which enhanced the photocatalytic quantum efficiency.