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Mass-selective photodissociation spectroscopy and quantum mechanical calculations were combined to study the photoinduced reactions of bidenate metal complexes. The calculations approximately reproduce the action spectra of the complexes and were valuable for shaping and sorting out the fairly sophisticated reaction mechanisms in large systems.

2,4-diaminobutyric acid (DAB), a newly identified algal toxins in water, pose a great threat to human health. DAB may react with chlorine or chloramine to produce CX 3 R-type disinfection by-products (DBPs) during water treatment processes. This study mainly investigated the formation and speciation of DBPs from chlor(am)ination of DAB. The results revealed that haloacetic acids (HAAs), trihalomethanes (THMs) and haloacetonitriles (HANs) were the main kinds of CX 3 R-type DBPs generated from DAB during chlor(am)ination, of which dichloroacetic acid yielded the highest. The formation and total toxicity of four CX 3 R-type DBPs from DAB during chloramination was significantly lower than that during chlorination at each Cl 2 :N molar ratio. However, more formation of Br-THMs and I-THMs were observed during chloramination in the presence of Br - /I - . Futhermore, the effects of chlor(am)ine dosage, solution pH, reaction time, and the concentration of Br - and I - on the formation and speciation of CX 3 R-type DBPs were also evaluated during chlor(am)ination. The plausible formation pathways of CX 3 R-type DBPs from DAB were proposed and verified by theoretical calculation. The quantum chemistry calculations indicate that 1N in DAB and 8N in 2,4-diaminochlorobutyric acid (C 4 H 9 O 2 N 2 Cl) were more likely to be attacked by electrophiles, supporting the proposed pathway schemes., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Chloride ion (Cl - ) is one of the most common anions in the aqueous environment. A mathematical model was developed to determine and quantify the impact of Cl - on the oxidization rate of organic compounds at the beginning stage of the UV/persulfate (PS) and UV/H 2 O 2 processes. We examined two cases for the UV/PS process: (1) when the target organic compounds react only with sulfate radicals, the ratio of the destruction rate of the target organic compound when Cl - is present to the rate when Cl - is not present (designated as r R Cl - / r R ) is no larger than 1.942%; and (2) when the target organic compounds can react with sulfate radicals, hydroxyl radicals and chlorine radicals, r R Cl - / r R , can be no larger than 60%. Hence, Cl - significantly reduces the organic destruction rate in the UV/PS process. In the UV/H 2 O 2 process, we found that Cl - has a negligible effect on the organic-contaminant oxidation rate. Our simulation results agree with the experimental results very well. Accordingly, our mathematical model is a reliable method for determining whether Cl - will adversely impact organic compounds destruction by the UV/PS and UV/H 2 O 2 processes.

Noble metals, like Ag and Au, are the most intensively studied plasmonic materials in the visible range. Plasmons in semiconductors, however, are usually believed to be in the infrared wavelength region due to the intrinsic low carrier concentrations. Herein, we observe the edge plasmon modes of Bi 2 Te 3 , a narrow-band gap semiconductor, in the visible spectral range using photoemission electron microscopy (PEEM). The Bi 2 Te 3 nanoplates excited by 400 nm femtosecond laser pulses exhibit strong photoemission intensities along the edges, which follow a cos 4 dependence on the polarization state of incident beam. Because of the phase retardation effect, plasmonic response along different edges can be selectively exited. The thickness-dependent photoemission intensities exclude the spin-orbit induced surface states as the origin of these plasmonic modes. Instead, we propose that the interband transition-induced nonequilibrium carriers might play a key role. Our results not only experimentally demonstrate the possibility of visible plasmons in semiconducting materials but also open up a new avenue for exploring the optical properties of topological insulator materials using PEEM.