•A facile method based on image binarization is introduced to calculate porosity.•The method is compared with two popular methods, to show higher accuracy.•The method is tested to show robustness under different brightness and contrast.•Mathematical derivation of porosity vs current is provided.Current methods to calculate porosity of tubular or porous structures are either inaccurate or complicated for operation. We introduce a facile method (M7) based on image binarization of top-view specimen images from scanning electron microscopy. M7 is both accurate and convenient, and shows high robustness regardless of external parameters like brightness or contrast. Relation between porosity and applied current during galvanostatic anodization is derived. The porosity-current relation differs in aqueous and organic solution, which can be explained as different conductivity of two electrolytes.Download high-res image (134KB)Download full-size image

•A facile method based on image binarization is introduced to calculate porosity.•The method is compared with two popular methods, to show higher accuracy.•The method is tested to show robustness under different brightness and contrast.•Mathematical derivation of porosity vs current is provided.Current methods to calculate porosity of tubular or porous structures are either inaccurate or complicated for operation. We introduce a facile method (M7) based on image binarization of top-view specimen images from scanning electron microscopy. M7 is both accurate and convenient, and shows high robustness regardless of external parameters like brightness or contrast. Relation between porosity and applied current during galvanostatic anodization is derived. The porosity-current relation differs in aqueous and organic solution, which can be explained as different conductivity of two electrolytes.Download high-res image (134KB)Download full-size image

•PAA with petal-like micropattern was fabricated in oxalic acid electrolyte.•Explanation for petal-like micropattern and nanofibers is proposed.•Shear and corrosion effects of micro-flow contribute to petal-like micropattern.•The self-ordering nanochannels of PAA are attributed to the oxide plastic flow.Special nanostructures of porous anodic alumina (PAA), such as the petal-like micropattern and nanofibers of alumina, cannot be explained by the classical field-assisted dissolution and dynamic equilibrium models. Here, by combination of oxygen bubble mould and plastic flow model, a reasonable explanation for these special nanostructures is proposed. The petal-like micropatterns of PAA and nanofibers of alumina are all clarified by the oxygen bubble mould and the plastic flow model. The self-ordering nanochannels of PAA are attributed to the oxide plastic flow around a gas bubble mould at each pore bottom. The petal-like micropatterns and nanofibers of alumina are attributed to chemical corrosion enhanced by the micro-gas-flow and micro-liquid-flow.Download high-res image (160KB)Download full-size image

•TiO2 nanotube arrays (TNTAs) are treated by a hydrothermal solid–gas method (HSGM).•HSGM can achieve TiO2 nanoparticles (NPs)/TNTAs hybrids with bigger surface areas.•Vapor pressure is a key factor to control morphology of TNTAs and HSGM reaction rate.•The NPs/TNTAs hybrid structure exhibits a big areal capacitance of 76.12 mF cm−2.•Areal capacitance and cycling stability are enhanced further via annealing in argon.Although TiO2 nanotube arrays (TNTAs) have shown great promise as supercapacitor materials, their specific capacitances are still not comparable with some typical materials. Here, TiO2 nanoparticles (NPs)/TNTAs hybrid structure has been derived from the anodized TNTAs by a facile hydrothermal solid-gas method (HSGM), which can avoid cracking or curling of the TNTAs from Ti substrate. The obtained NPs/TNTAs hybrid structure can exhibit a ∼4.90 times increase in surface area and a ∼5.49 times increase in areal specific capacitance compared to the TNTAs without HSGM treatment. Besides, the argon-atmosphere annealing can offer improved areal capacitance and cycling stability relative to the air-atmosphere annealing. The hydrothermal vapor pressure is a key factor for controlling microscopic morphologies of TNTAs, the morphology transformations of TNTAs during the HSGM treatment can be accelerated under enhanced vapor pressures. The highest areal capacitance of HSGM-treated TNTAs is up to 76.12 mF cm−2 at 0.5 mA cm−2, well above that of any TiO2 materials reported to date.Download high-res image (394KB)Download full-size image

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) with three to five aromatic rings have been documented to ubiquitously occur in environmental matrices. In this study, residual concentrations and profiles of 20 individual ClPAHs were determined in 35 surface sediment samples from Maowei Sea, a semi-enclosed shallow inland bay located in the northwestern part of South China Sea. The concentrations of ΣClPAHs in sediment ranged from 313 to 9650 pg/g dw with a detection rate of 43–100%. Of the individual ClPAH congeners, 9-ClPhe was the most abundant in Maowei Sea with the concentrations that ranged from 99.9 to 3610 pg/g dw (mean 1120 pg/g dw). High-molecular-weight ClPAH congeners (four to five rings) were predominant in sediments from sampling locations near a petrochemical industrial complex, whereas low-molecular-weight ClPAH congeners (three rings) were predominant in sediments from estuarine and mangrove locations. A positive matrix factorization (PMF) model in combination with dioxin-like toxic equivalency quotient (TEQ) results was used to apportion sources of ClPAHs. Vehicular emission, combustion/chemical industrial processes, and two other unknown sources accounted for 40.1, 25.5, 20.8, and 13.6%, respectively, of ClPAH sources in sediment; their contribution to TEQs in sediments were 24.2, 40.5, 19.3, and 16.0%, respectively. Further investigations are needed to elucidate potential sources and ecological risks of ClPAHs in sediments.

⿢The influences of H2O2 and H2O on the morphologies and anodizing current were compared.⿢The formation mechanism of ginseng-like nanotubes is proposed for the first time.⿢The thickness of barrier oxide is inversely proportional to equilibrium ionic current.⿢The relationships between the morphologies and ionic current were analyzed quantitatively.Anodic TiO2 nanotubes (ATNTs) have been investigated extensively. However, the relationship between anodizing curves and the morphologies cannot be explained or quantified by the filed-assisted dissolution theory or plastic flow models. Here, influences of H2O2 and H2O content on anodizing current and morphology of ATNTs were explored and compared in detail. With H2O2 addition, the ginseng-like nanotubes were formed and the anodizing current increased a lot. Based on the oxygen bubble mould, the formation mechanism of the ginseng-like nanotubes has been proposed. Moreover, H2O addition causes an opposite current variation trend to H2O2 addition. The relationships between the morphologies and the anodizing curves were clarified quantitatively by the simulation of the ionic current and electronic current. H2O2 addition accelerates oxygen evolution and therefore electronic current increases with H2O2 content. Moreover, nanotube diameter increases with H2O content mainly due to the dilution of the F⿿ anions and the thicker barrier oxide.

Eight Polybrominated diphenyl ether (PBDE) congeners (BDE 28, 47, 99, 100, 153, 154, 183 and 209) were determined to examine the hair burden at low concentrations, and the relationship between PBDE concentrations in human hair and indoor dust from a college environment (Shanghai University campus). Chemical analyses showed that the total concentrations of PBDEs in hair ranged from 4.04 to 99 ng/g dw, and were found to be fourfold higher in females than in males (p < 0.05). The total PBDEs concentrations in indoor dust samples ranged from 170 to 1,360 ng/g dw. Significantly positive correlations were observed between human hair and indoor dust for BDE 47 (r = 0.44, p = 0.048) and BDE 99 (r = 0.68, p = 0.025). However, no significant association was noted between other PBDE congeners in human hair and indoor dust in the present study.