The sorption behavior of four hydrophobic organic contaminants (HOCs) (i.e., phenanthrene, naphthalene, lindane, and 1-naphthol) by three types of polymers namely polyethylene (PE), polystyrene (PS), and polyphenyleneoxide (PPO) was examined in this work. The organic carbon content-normalized sorption coefficients (K(oc)) of phenanthrene, lindane, and naphthalene by PEs of same composition but distinct physical makeup of domains increased with their crystallinity reduction (from 58.7 to 25.5%), suggesting that mobility and abundance of rubbery domains in polymers regulated HOC sorption. Cross-linking in styrene-divinylbenzene copolymer (PS2) created substantial surface area and porosity, thus, K(oc) values of phenanthrene, lindane, naphthalene, and 1-naphthol by PS2 were as high as 274.8, 212.3, 27.4, and 1.5 times of those by the linear polystyrene (PS1). The K(oc) values of lindane, naphthalene, and 1-naphthol by polar PPO were approximately 1-3 orders of magnitude higher than those by PS1, and PPO had comparable sorption for phenanthrene but higher sorption for naphthalene and 1-naphthol than PS2. This can be a result that a portion of O-containing moieties in PPO were masked in the interior part, while leaving the hydrophobic domains exposed outside, therefore demonstrating the great influence of the spatial arrangement of domains in polymers on HOC sorption.

Highly uniform silver orthophosphate microcrystals with novel tetrapod morphology are, for the first time, synthesized via a simple hydrothermal route with the assistance of urea. The effect of active crystal facets on the photocatalytic activity is principally investigated. The silver orthophosphate tetrapods exhibit significantly higher visible light activity than the polyhedrons for the degradation of toxic organic compounds due to the highly exposed {110} facets.Morphology control of photocatalysts has been considered to be one of the most promising avenues to improve their photocatalytic properties. [1][2][3][4][5] For example, various TiO 2 nanostructures including nanotubes, 3 nanosheets, 4 and nanorods 5 have been designed and synthesized, all of which exhibit higher activity than P25. However, its relatively wide band gap limits the photocatalytic applications under visible light irradiation. Therefore, it is desirable and compulsory to explore efficient visible-light-driven photocatalysts. Recently, silver orthophosphate (Ag 3 PO 4 ) has been demonstrated to be an active photocatalyst for the degradation of organic pollutants and the oxidation of water under visible light. 6,7 Specifically, Ag 3 PO 4 photocatalysts are reported to achieve a quantum efficiency up to 90% at wavelengths longer than 420 nm. 8 The research of Ag 3 PO 4 is thus attracting considerable interest. Up to now, many efforts have been devoted to further improving and optimizing their photoelectric and photocatalytic properties by means of semiconductor coupling 8,10-12 and polymer composites. 13 However, most of the as-mentioned researches mainly focus on the modification of Ag 3 PO 4 . It is well known that the morphology of materials is closely related to the exposed facets of the crystals, which directly affect the properties of the catalysts. 4b,c In this aspect, Ye and co-workers have succeeded in

As nanotechnology-based products enter into widespread use, nanomaterials will end up in disposal waste streams that are ultimately discharged to the environment. One possible end-of-life scenario is incineration. This review attempts to ascertain the potential pathways by which nanomaterials may enter incinerator waste streams and the fate of these nanomaterials during the incineration process. Although the literature on incineration of nanomaterials is scarce, results from studies of their behavior at high temperature or in combustion environments for other applications can help predict their fate within an incinerator. Preliminary evidence suggests nanomaterials may catalyze the formation or destruction of combustion by-products. Depending on their composition, nanomaterials may undergo physical and chemical transformations within the incinerator, impacting their partitioning within the incineration system (e.g., bottom ash, fly ash) and the effectiveness of control technology for removing them. These transformations may also drastically affect nanomaterial transport and impacts in the environment. Current regulations on incinerator emissions do not specifically address nanomaterials, but limits on particle and metal emissions may prove somewhat effective at reducing the release of nanomaterials in incinerator effluent. Control technology used to meet these regulations, such as fabric filters, electrostatic precipitators, and wet electrostatic scrubbers, are expected to be at least partially effective at removing nanomaterials from incinerator flue gas.

No abstract

Suspension of the pristine and COOH-substituted multi-walled carbon nanotubes (P- and C-MWCNTs) with different outer diameters (ODs) by humic acids (HAs) from a peat soil was examined. Under shaking condition, MWCNTs were not suspended within 5 d. Without HAs, C-MWCNTs were slightly suspended by sonication within 16 h, but no suspension was observed for the pristine ones (P-MWCNTs). HAs greatly enhanced suspension of both P- and C-MWCNTs. The suspension enhancement was attributed to HA sorption, which increased electrostatic repulsion and steric hindrance between individual MWCNTs. Introduction of O-containing hydrophilic moieties to MWCNTs via HA sorption enhanced the interactions of their surfaces with water through H-bonding. Suspending capability of various MWCNTs on suspended mass concentration basis by four HAs showed inconsistent orders with the increasing or decreasing trend of their ODs. However, the suspended surface area concentrations of both P- and C-MWCNTs by individual HAs consistently followed an order of P8 > P30 > P50, and C8 > C30 > C50 (P and C, respectively, refer to P- and C-MWCNTs, and the numbers represent their ODs). These data implied that MWCNTs with smaller OD could be more strongly suspended by a given HA relative to those with larger OD under sonication condition.

No abstract

Catalyst-free, vertical array of InAs nanowires (NWs) are grown on Si (111) substrate using MOCVD technique. The as-grown InAs NWs show a zinc-blende crystal structure along a < 111 > direction. It is found that both the density and length of InAs NWs decrease with increasing growth temperatures, while the diameter increases with increasing growth temperature, suggesting that the catalyst-free growth of InAs NWs is governed by the nucleation kinetics. The longitudinal optical and transverse optical (TO) mode of InAs NWs present a phonon frequency slightly lower than those of InAs bulk materials, which are speculated to be caused by the defects in the NWs. A surface optical mode is also observed for the InAs NWs, which shifts to lower wave-numbers when the diameter of NWs is decreased, in agreement with the theory prediction. The carrier concentration is extracted to be 2.25 × 1017 cm-3 from the Raman line shape analysis. A splitting of TO modes is also observed.PACS: 62.23.Hj; 81.07.Gf; 63.22.Gh; 61.46.Km

Carbon dots (C dots, size < 10 nm) have been conventionally decorated onto semiconductor matrixes for photocatalytic H evolution, but the efficiency is largely limited by the low loading ratio of the C dots on the photocatalyst. Here, we propose an inverse structure of CdZnS quantum dots (QDs) loaded onto the onionlike carbon (OLC) matrix for noble metal-free photocatalytic H evolution. CdZnS QDs (6.9 nm) were uniformly distributed on an OLC (30 nm) matrix with both upconverted and downconverted photoluminescence property. Such an inverse structure allows the full optimization of the QD/OLC interfaces for effective energy transfer and charge separation, both of which contribute to efficient H generation. An optimized H generation rate of 2018 μmol/h/g (under the irradiation of visible light) and 58.6 μmol/h/g (under the irradiation of 550-900 nm light) was achieved in the CdZnS/OLC composite samples. The present work shows that using the OLC matrix in such a reverse construction is a promising strategy for noble metal-free solar hydrogen production.