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Abstract: Pt/TiO2 derived from complete decomposition of the surface-anchored Pt(dcbpy)Cl2 (dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) precursor (denoted as C-Pt/TiO2) was prepared to serve as photocatalyst in visible light region. For dye-sensitized hydrogen production experiments, the photocatalyst was sensitized by Ru(2,2′-bipyridine-4,4′-dicarboxylic)2(NCS)2 (the N3 dye) and Ru(2,2′bipyridyl-4,4′-dicarboxylic) (4,4′- dinonyl-2,2′bipyridine) (NCS)2 (the Z907 dye) to induce hydrogen evolution in the presence of sacrificial electron donor, triethanolamine (TEA). The hydrogen generation results showed that C-Pt/TiO2 was found to be a much more active photocatalyst when compared to P-Pt/TiO2, prepared by conventional method of photochemical deposition of H2PtCl6 (denoted as P-Pt/TiO2). For further investigation, the photodegradation experiments in visible region were also confirmed the better photocatalytic activity of C-Pt/TiO2. The enhanced catalytic activity is due to efficient interparticle electron transfer with the small-size and high-disperse platinum particles generated from photodeposition of Pt(dcbpy)Cl2, which was verified by the transmission electron microscopy (TEM) measurement. [Copyright &y& Elsevier]

Carbamate insecticides, which are common micropollutants in surface waters, were found to generate dichloromethlyamine (DCMA) during chlorination. DCMA formation from other precursors has been reported previously; it is part of the emerging class of nitrogen-based disinfection byproducts (N-DBPs) of health concern in chlorinated water. However, there is a limited understanding about its formation, stability, and toxicity. Four carbamate insecticides (methomyl, carbofuran, carbaryl, and thiodicarb) were examined as DCMA precursors over a range of reaction conditions, based on variables of chlorine/precursor (Cl/P) molar ratio, pH, time, and temperature. DCMA was found to be the dominant volatile DBP to result from chlorination of all four carbamate insecticides, with molar yields ranging from 12% to 150% at a Cl/P molar ratio of 20. Further experiments indicated CH 3 NCl 2 to be relatively stable, with a half-life of up to 35 h in water. The toxicity of CH 3 NCl 2 was investigated using a bacterial bioluminescence inhibition test and survival of human lung tumor cells. The results of these toxicity assays indicated that CH 3 NCl 2 is about 3 orders of magnitude more toxic than CHCl 3 . CH 3 NCl 2 concentrations in the ppb range were observed to result from chlorination of surface water or tap water samples collected from several different locations in China. The results suggest that precursors to CH 3 NCl 2 formation are ubiquitous and that CH 3 NCl 2 poses a hazard to public health and the environment and should be considered in disinfection chemistry and water treatment.

Buckminsterfullerenes (C 60 ) are widely used nanomaterials that are present in surface water. The combination of C 60 and humic acid (HA) generates reactive oxygen species (ROS) under solar irradiation, but this process is not well understood. Thus, the present study focused on the photochemical formation of singlet oxygen ( 1 O 2 ), hydroxyl radical (HO • )-like species, superoxide radicals (O 2 •- ), hydrogen peroxide (H 2 O 2 ), and triplet excited states ( 3 C 60 */ 3 HA*) in solutions containing both C 60 and HA. The quantum yield coefficients of excited triplet states (f TMP ) and apparent quantum yields of ROS were measured and compared to the calculated values, which were based on the conservative mixing model. Although C 60 proved to have only a slight impact on the 1 O 2 formation from HA, C 60 played a key role in the inhibition of O 2 •- . The photochemical formation of H 2 O 2 followed the conservative mixing model due to the reaction of C 60 •- with HO 2 • /O 2 •- , and the biomolecular reaction rate constant has been measured as (7.4 ± 0.6) × 10 6 M -1 s -1 . The apparent f TMP was significantly lower than the calculated value, indicating that the steric effect of HA was significant in the reaction of 3 C 60 * with the TMP probe. In contrast, C 60 did not have an effect on the photochemical formation of HO • from HA, suggesting that HO • is elevated from the hydrophilic surface of HA. The aforementioned results may be useful for predicting the photochemical influence of C 60 on aqueous environments.