Combined water pollution with the coexistence of heavy metals and organic contaminants is of great concern for practical wastewater treatment. In this study, a jaboticaba-like nanocomposite, titanate nanotubes supported TiO2 (TiO2/TiNTs), was synthesized by a two-step hydrothermal treatment. TiO2/TiNTs had large surface area, abundant of –ONa/H groups and fine crystal anatase phase, thus exhibited both good adsorptive performance for Cu(II) and high photocatalytic activity for phenanthrene degradation. The maximum Cu(II) adsorption capacity on TiO2/TiNTs was 115.0 mg/g at pH 5 according to Langmuir isotherm model, and >95% of phenanthrene was degraded within 4 h under UV light. TiO2/TiNTs showed about 10 times higher observed rate constant (kobs) for phenanthrene degradation compared to the unmodified TiNTs. More importantly, the coexistence of Cu(II) promoted photocatalytic degradation of phenanthrene, because the incorporated Cu(II) in the lattice of TiNTs could trap photo-excited electron and thus inhibited the electron-hole recombination. Density functional theory (DFT) calculation indicated that the sites of phenanthrene with high Fukui index (f0) preferred to be attacked by OH radicals. The quantitative structure–activity relationship (QSAR) analysis revealed that the degradation intermediates had lower acute toxicity and mutagenicity than phenanthrene. TiO2/TiNTs also owned high stability, as only slight loss of Cu(II) and phenanthrene removal efficiency was observed even after four reuse cycles. The developed material in this study is of great application potential for water or wastewater treatment with multi-contaminants, and this work can help us to better understand the mechanisms on reaction between Ti-based nanomaterials and different kinds of contaminants.
Conventional gyrotron backward-wave oscillators (gyro-BWOs) operate in a low-order mode, e.g., TE 0,1 mode. As the operating frequency extends to the terahertz (THz) band, the transverse size of low-order mode cavity shrinks, and the power capability is reduced, consequently. A solution to adopt an overmoded interaction cavity with a significantly enlarged index of the operating mode is valid on the condition that the challenging problem of mode competition can be controlled during the broadband frequency tuning. In this paper, a high-order whispering-gallery mode (WGM) THz gyro-BWO with a cathode-end output circuit is investigated. A segment-tapered circuit is applied to suppress the Q factors of competing modes and to obtain a the competition-free stable start-oscillation scenario. The theoretical result predicts that the effective frequency tuning range continuously covers between 252.3 and 260 GHz when the B-field is changed from 9.41 to 9.96 T. Our studies are beneficial to the development of high-performance sources for THz biomedical and material science applications.
Ternary solar cells have been proven to be an effective way to increase the power conversion efficiency (PCE) of organic solar cells (OSCs). Up to now, research effort has mostly focused on fullerene derivatives and acceptor–donor–acceptor (A–D–A) type non-fullerene acceptor-based ternary solar cells, while perylene diimide (PDI)-based ternary devices have been rarely studied. In this contribution, we introduced a new type of ternary solar cell based on a PDI-based small-molecule acceptor (PBI-Por) and a polymer donor (PTB7-Th) with a third PDI-based polymer acceptor (PDI-V). The introduction of PDI-V into the ternary blends not only broadens the absorption of blend films but also increases the electron mobilities. As a result, a high efficiency of 9.43% was obtained for the ternary OSC, which is 20% higher than that of the binary OSC. Detailed studies indicate that PDI-V showed good compatibility with PBI-Por in the blend films, which demonstrates a promising way to fabricate high-performance PDI-based OSCs.
