Multi-Scale Engineered 2D Carbon Polyhedron Array with Enhanced Electrocatalytic Performance.

Electrocatalyst engineering from the atomic to macroscopic level of electrocatalysts is one of the most powerful routes to boost the performance of electrochemical devices. However, multi-scale structure engineering mainly focuses on the range of atomic-to-particle scale such as hierarchical porosity engineering, while catalyst engineering at the macroscopic level, such as the arrangement configuration of nanoparticles, is often overlooked. Here, a 2D carbon polyhedron array with a multi-scale engineered structure via facile chemical etching, ice-templating induced self-assembly, and high-temperature pyrolysis processes is reported. Controlled phytic acid etching of the carbon precursor introduces homogeneous atomic phosphorous and nitrogen doping, as well as a well-defined mesoporous structure. Subsequent ice-templated self-assembly triggers the formation of a 2D particle array superstructure. The atomic-level doping gives rise to high intrinsic activity, while the well-engineered porous structure and particle arrangement addresses the mass transport limitations at the microscopic particle level and macroscopic electrode level. As a result, the as-prepared electrocatalyst delivers outstanding performance toward oxygen reduction reaction in both acidic and alkaline media, which is better than recently reported state-of-the-art metal-free electrocatalysts. Molecular dynamics simulation together with extensive characterizations indicate that the performance enhancement originates from multi-scale structural synergy.

Characteristics, sources and health risks of toxic species (PCDD/Fs, PAHs and heavy metals) in PM2.5 during fall and winter in an industrial area.

Particulate toxic species, such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals may have significant health risks. This study investigated characteristics, sources and health risks of all three classes of toxic species in PM2.5 (particles with aerodynamic diameter ≤2.5 µm) samples collected at an industrial area in Changzhou, a big city in the Yangtze Delta region of China. Fourteen heavy metals altogether constituted 2.87% of PM2.5 mass, with Fe, Al and Zn as the major elements. Principal component analysis (PCA) suggested that heavy metals came from four sources: vehicles, industry, crustal dust, mixed coal combustion and industrial process. The daily average concentration of 18 PAHs was 235.29 ng/m3, accounting for 0.21% of PM2.5 mass. The dominant PAHs were high molecular weight ones, contributing 73.5% to the total PAHs. Diagnostic analyses indicated that sources of PAHs included vehicle/coal combustion and petroleum emissions, wherein diesel emission played a more important role than gasoline emission. PCA showed that the largest contributor of PAHs was vehicle exhaust mixed with coal combustion, followed by three industry-related sources. Total concentration of 17 PCDD/Fs varied between 3.14 and 37.07 pg/m3, with an average of 14.58 pg/m3. The 10 PCDFs accounted for 70.5% of total concentration of 17 PCDD/Fs. Health risk assessments showed that the carcinogenic risk of heavy metals was acceptable, while risks from PAHs and PCDD/Fs cannot be ignored. Back trajectory analysis indicated that local/regional transported air masses from northern China was the major source areas of the toxic species.

Source contributions to total concentrations and carcinogenic potencies of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in ambient air: a case study in Suzhou City, China.

The potential source categories and source contributions of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in ambient air from Suzhou City, China, were performed by principal component analysis-multiple linear regression (PCA-MLR) and positive matrix factorization (PMF). The carcinogenic potencies of PCDD/Fs were quantitatively apportioned based on the positive matrix factorization-toxic equivalent concentration (PMF-TEQ) method. The results of the present study were summarized as follows. (1) The total concentrations and toxic equivalent concentrations of PCDD/Fs (∑PCDD/Fs and TEQ) in ambient air from Suzhou City were 1.34-42.80 pg N m-3 and 0.081-1.22 pg I-TEQ N m-3, respectively. (2) PCA-MLR suggested that industrial combustion (IC), electric arc furnaces (EAFs) and secondary aluminum smelters (ALSs), unleaded gas-fueled vehicle sources (UGFVs), ALSs, and hazardous solid waste incinerators (HSWIs) could be the primary PCDD/F contributors, accounting for 13.2, 16.7, 35.5, 19.4, and 15.2% of ∑PCDD/Fs, respectively. (3) PMF and PMF-TEQ indicated that EAFs (carbon steel), UGFVs, IC, ALSs, municipal solid waste incinerators (MSWIs) and hospital waste incinerators (HWIs), and HSWIs contributed 10.9, 10.9, 42.8, 11.3, 10.7, and 13.4% to ∑PCDD/Fs, but contributed 8.3, 12.3, 50.3, 12.7, 6.0, and 10.4% to carcinogenic potencies of PCDD/Fs. This study was the first attempt to quantitatively apportion the source-specific carcinogenic potencies of PCDD/Fs in ambient air.

Investigation of submicron aerosol characteristics in Changzhou, China: Composition, source, and comparison with co-collected PM2.5.

Mass concentrations and chemical compositions of submicron particles (PM1) collected during July 2015 to April 2016 in Changzhou, a city in the Yangtze River Delta region, were systematically investigated for the first time. Specifically, an Aerodyne soot particle aerosol mass spectrometer (SP-AMS) was employed to characterize the water-soluble organic matter (WSOM). The average concentration of PM1 was 63.6 µg m-3, occupying ∼60% of co-collected PM2.5 mass. Water soluble inorganic ions (WSIIs) was the most abundant component with secondary ions (SO42-, NO3- and NH4+) as the dominant species. Organic matter (OM) accounted for 21.6% of PM1, with approximately 80% was water-soluble. Trace metals could constitute up to 3.0% of PM1 mass, and Fe, Al and Zn were the three most abundant ones. PAHs were predominated by ones with 5-6 rings, occupying over half of the PAHs mass; further analyses showed that fuel and coal combustion had significant contributions to PAHs. Positive matrix factorization of the WSOM data separated four factors: a traffic-related hydrocarbon-like OA (HOA), a local OA (LOA) likely associated with cooking and coal combustion emissions, etc., a secondary nitrogen-enriched OA (NOA) and an oxygenated OA (OOA). PCA analyses showed that crustal source was likely important for PM1 too. Back trajectory results implied that both PM1 and PM2.5 were mainly derived from local/regional emissions. Our findings present results regarding the PM1 chemistry and its relationship with the PM2.5 in Changzhou, which are valuable for the government to make effective policies to reduce the aerosol pollution in and near the city.

[Pollution Characteristics and Source Identification of PAHs in Atmospheric PM2.5 in Changzhou City].

A total of 55 ambient fine particle (PM2.5) samples were collected in Changzhou City from January to August 2016. The concentrations of 17 PM2.5-bound PAHs in the samples were analyzed by GC-MS. Results showed that seasonal average mass concentrations of PAHs in winter, spring, and summer were 140.24, 41.42, and 2.96 ng·m-3, respectively, which indicating that the pollution of PAHs in winter appeared more serious than in the other two seasons, and 4-6-ring high molecular weight PAHs were predominant in all three seasons. The average daily level of BaP was 3.64 ng·m-3 and the days it exceeded the permitted standard accounted for 41% of total days. PAH concentration had significant negative correlations with temperature (correlation coefficient: -0.643) and visibility (correlation coefficient: -0.466), whereas it had good positive correlations with atmospheric pressure (correlation coefficient: 0.544) and poor correlations with wind speed and relative humidity. PAH concentrations were higher at nighttime than at daytime, because of the influences of temperature difference, atmospheric stratification, as well as pollution sources. The results from the air backward trajectory model indicated that PM2.5-bound PAHs in Changzhou were mainly affected by local emission sources and short-distance transportation, whereas the contribution of long-distance transmission was small (only 11%). Based on analysis of characteristic ratios, PAHs were mainly sourced from coal burning, vehicle emissions, and biomass burning. An incremental lifetime cancer risk (ILCR) model was used to evaluate the health impact of PAHs via breathing exposure pathways. Results revealed that the ILCR of adults was higher than that of children. The ILCRs of the group for winter and spring were slightly higher than the risk threshold, but a difference was not obvious for summer.

[Kinetics of alkylphenols degradation in aqueous phase with excilamp irradiation].

The 206 nm irradiation from excilamp was able to directly photo-degrade 4-nonylphenol (4-NP) and 4-octylphenol (4-OP), but it could not oxidize them completely into CO2. Under the same irradiation condition, the removal efficiency of 4-OP was higher than that of 4-NP. Pseudo-first order kinetic model and modified kinetic model were used to fit the kinetics of photo-degradation process, and the direct photolysis rate constants under 206 nm UV irradiation were obtained. The experimental results demonstrated that the photolysis rate constant was higher at lower initial concentration of alkylphenols. Two kinetic models were appropriate for the direct photolysis of alkylphenols at low concentration, but the modified model did not fit for high concentrations. Degradation rate can be obviously enhanced when adding H2O2 into the reaction, but the TOC removal was distinct only when the dosage of H2O2 was high. At last, we concluded that the direct photolysis rate constant k(d) was 0.032 8 min(-1) and the reaction rate constant k(pH) between 4-OP and H2O2 was 17.4520 L x (mol x min)(-1).

Analysis of eupatilin-human serum albumin interactions by means of spectroscopic and computational modelling.

The interaction of eupatilin (5,7-dihydroxy-3',4',6-trimethoxyflavone) with human serum albumin (HSA) was studied at simulative physiological pH, with a HSA concentration of 3.0 x 10(-6)mol L(-1) and eupatilin concentrations over the range of 6.0 x 10(-6) to 1.9 x 10(-5) mol L(-1). Fluorescence spectroscopy in combination with UV absorption spectroscopy and Fourier transform infrared (FTIR) spectroscopy were used to study the binding properties (including binding mechanism, the binding constants, the number of binding sites and the binding mode) of the interaction of eupatilin with HSA and the effect of this drug on HSA conformation changes. According to the Scatchard equation there was only one class of binding site that could bind to HAS; the binding constants were 1.53 x 10(5), 1.20 x 10(5), 1.05 x 10(5), 0.87 x 10(5) L mol(-1) at temperatures of 287, 298, 310 and 318 K, respectively. The FTIR spectra revealed that the protein secondary structure changed, with reductions in alpha-helices of about 3.65% at a drug to protein molar ratio of 3. The thermodynamic analysis (enthalpy and entropy change: DeltaH(0) and DeltaS(0)) and the computational modelling study indicated that hydrophobic force played an important role in eupatilin-HSA complex stabilization, and eupatilin could bind within the subdomain IIA of HSA.

Stereoselective degradation kinetics of theta-cypermethrin in rats.

The enantioselective degradation and chiral conversion of theta-cypermethrin (TCYM) in rats have been studied via intravenous (i.v.) injection. The degradation kinetics and the enantiomer fraction (EF) were determined by means of normal-phase high-performance liquid chromatography (HPLC) with diode array detection (DAD) and a cellulosetris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP). The degradation followed pseudo-first-order kinetics. The degradation of the (+)-TCYM was much faster than that of the (-)-TCYM in plasma, heart, liver, kidney, and fat after administration of racemic TCYM (rac-TCYM). The EFs were over 0.500 in these tissues and muscle. The results showed the conversion of (+)-enantiomer to (-)-enantiomer in plasma after injection of (-)- and (+)-TCYM separately. The results for the major differences in the degradation of the enantiomers may have some implication for the environmental and ecological risks assessment for chiral pesticides.

Determination of Etofenprox in environmental samples by HPLC after anionic surfactant micelle-mediated extraction (coacervation extraction).

A method is described for determination of residues of the insecticide Etofenprox in environmental samples. Anionic surfactant micelle-mediated extraction (coacervation extraction) was evaluated for isolation of Etofenprox before HPLC. The optimum conditions used for extraction included: 0.09 g sodium dodecanesulfonate (SDoS), 3.1 mL (3.3, for concentrations below 0.04 mg L(-1)) 12 mol L(-1) HCl, 5 min vortex stirring, 5 min centrifugation at 4000 rpm, 2 h equilibration time. The limits of quantification (LOQ) and detection (LOD) were 0.01 and 0.004 mg L(-1), respectively, and recoveries obtained from five real samples ranged from 94.33+/-2.48 to 100.13+/-2.71%. The precision of the method was good; relative standard deviations (RSD) were less than 7%.