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Coiled amorphous carbon nanotube (CACNT) array was prepared by chemical vapor deposition method. The experimental results indicated that the length of as-prepared CACNT array was about 30 μm. The electromagnetic wave absorbing properties were studied through comparison among CACNTs, CACNT-La(NO 3 ) 3 , CACNT-(Fe, Co, Ni) and CACNT-reduced graphene oxide (RGO). The experimental results showed the maximum frequency bandwidth of CACNT-(Fe, Co, Ni) was 6.4 GHz below −5 dB and 2.3 GHz below −10 dB separately. Compared to the pure CACNTs, all the frequency bandwidth had been broaden after adding the modified agent. Meanwhile, the additive of rare earth ions La 3+ could effectively increase the maximum absorption peak (−17.94 dB at 8.96 GHz). [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) have attracted broad attention due to their special optical properties and promising prospect in medical and biological applications. However, the process of QDs on cell membrane is worth further investigations because such process may lead to harmful effects on organisms and also important for QD application. In this study, adhesion of amino- and carboxyl-coated CdTe QDs (A-QDs and C-QDs) on cell membrane and the subsequent internalization are studied using a series of endocytosis-free model membranes, including giant and small unilamellar vesicles, supported lipid bilayers and giant plasma membrane vesicles (GPMVs). The adhered QD amounts on model membranes are quantified by a quartz crystal microbalance. The CdTe QD adhesion on model membranes is governed by electrostatic forces. Positively charged A-QDs adhere on GPMV surface and passively penetrate the plasma membrane via endocytosis-free mechanism, but negatively charged C-QDs cannot. Rat basophilic leukemia (RBL-2H3) cells are exposed to CdTe QDs to monitor the QD internalization process. Both A- and C-QDs are internalized by RBL-2H3 cells mainly via endocytosis. CdTe QDs do not accumulate on the plasma membrane of living cells due to the fast endocytosis and the weakened electrostatic attraction in biological medium, resulting in low chance of passive penetration. The suspended cells after trypsin digestion take more QDs than the adherent cells. A-QDs cause lower cell viability than C-QDs, probably because the approach of positively charged QDs to cells is favored and the smaller aggregates of A-QDs. [ABSTRACT FROM AUTHOR]

Silica nanoparticles (SiO 2 NPs) can cause health hazard after their release into the environment. Adsorption of natural organic matter and biomolecules on SiO 2 NPs alters their surface properties and cytotoxicity. In this study, SiO 2 NPs were treated by bovine serum albumin (BSA) and humic acid (HA) to study their effects on the integrity and fluidity of model cell membranes. Giant and small unilamellar vesicles (GUVs and SUVs) were prepared as model cell membranes in order to avoid the interference of cellular activities. The microscopic observation revealed that the BSA/HA treated (BSA-/HA-) SiO 2 NPs took more time to disrupt membrane than untreated-SiO 2 NPs, because BSA/HA adsorption covered the surface Si OH/Si O - groups and weakened the interaction between NPs and phospholipids. The deposition of SiO 2 NPs on membrane was monitored by a quartz crystal microbalance with dissipation (QCM-D). Untreated- and HA-SiO 2 NPs quickly disrupted the SUV layer on QCM-D sensor; BSA-SiO 2 NPs attached on the membranes but only caused slow vesicle disruption. Untreated-, BSA- and HA-SiO 2 NPs all caused the gelation of the positively-charged membrane, which was evaluated by the generalized polarity values. HA-SiO 2 NPs caused most serious gelation, and BSA-SiO 2 NPs caused the least. Our results demonstrate that the protein adsorption on SiO 2 NPs decreases the NP-induced membrane damage. [ABSTRACT FROM AUTHOR]

Low–cost activated carbon fiber composites (ACFCs) were explored as the basis for a system to remove NH 3 from the gas phase. ACFCs were synthesized by chemically activating a phenolic precursor on a glass fiber substrate using ZnCl 2 as catalyst. Additionally, ACFCs were oxidized with concentrated nitric acid at both room temperature and 83 °C to increase the density of surface oxygen groups. Commercially available phenolic-based physically activated carbon fibers were also oxidized under the same condition as a benchmark. Both physical properties and surface chemical properties of these materials were characterized using SEM, BET, elemental analysis, FTIR, XPS, and Boehm titration. Dynamic flowthrough NH 3 adsorption was measured at 500 ppm, at both 0% and 50% relative humidity. Results suggest ACFCs exhibit high surface area, rich oxygen functional groups, with post-treatment further improving surface oxygen content. ACFCs displayed fast sorption kinetics and high NH 3 adsorption capacity up to 50 mg/g. Acidic oxygen groups at the surface are correlated with ammonia adsorption. A new anhydride-based reaction mechanism was identified and is proposed, collectively with carboxylic acid functional groups, as being primarily responsible for retaining NH 3 . [ABSTRACT FROM AUTHOR]

Novel hybrid strong anion exchange porous carbon fibers (HACAX) were synthesized and evaluated for adsorption of low concentrations of Cr(VI) at natural pH. Positive surface charge due to pyridinium groups enables HACAX to adsorb Cr(V) rapidly and with high capacity. HACAX showed stable and regenerable performance for adsorbing and converting Cr(VI) into Cr(III) with no change in pH, which is attributed to the catalytic activity of surface oxygen functional groups. [ABSTRACT FROM AUTHOR]

Highlights: [•] Reactivation process involves a trigonal bipyramidal structure. [•] The rate-determining step of reactivation process was provided. [•] The H2Oθ-Glu pathway is more feasible for aging process. [•] The electrostatic influences of surrounding amino acids were exhibited. [ABSTRACT FROM AUTHOR]

The degradation of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere can lead to toxic derivatives which contribute to the carcinogenic potential of particulate organic matter. This paper aimed to investigate the mechanism of the OH-initiated oxidation degradation of benzo[α]pyrene (BaP), a cancer risk indicator. High-accuracy molecular orbital calculations were carried out, and all of the possible degradation pathways were discussed. The theoretical results were compared with the available experimental observation. The possible secondary reactions were also investigated. The rate constants of the crucial elementary steps were evaluated by using the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The dominant degradation products involve benzo[α]pyren-ol, nitro-benzo[α]pyrene, benzo[α]pyrene-7,10-dione as well as several ring-opened products such as alkyl substituted benzanthraldehyde et al. In particular, water plays an important role in the degradation pathways leading to the formation of nitro-benzo[α]pyrene. This work provides a comprehensive investigation of the OH-initiated degradation of BaP and should help to clarify its potential risk. [ABSTRACT FROM AUTHOR]

OH radical-initiated atmospheric oxidation of ethyl acrylate (ethyl 2-propenoate, EA) has been investigated by performing density functional theory (DFT) calculations. Optimizations of the reactants, intermediates, transition states and products were carried out at the MPWB1K/6-31+G(d,p) level. Single-point energy calculations were performed at the MPWB1K/6-311+G(3df,2p) level of theory. The detailed oxidation mechanism was presented and discussed. The results show that the OH addition is more energetically favorable than the H abstraction. Rice–Ramsperger–Kassel–Marcus (RRKM) theory was used to predict the rate constants over the possible atmospheric temperature range of 180–370 K. The Arrhenius expression adequately describes the total rate constant: k (EA+OH) = (1.71 × 10 −12 )exp(805.42/ T ) cm 3 molecule −1 s −1 . At 298 K, the atmospheric lifetime of ethyl acrylate determined by OH radicals is about 16.2 h. In order to find out the effect of alkyl substitution on the reaction activity, rate constants for the reactions of methyl acrylate, methyl methacrylate and butyl acrylate with OH radicals were also discussed. Calculation results show that the reaction activity may increase with the increased electron-donating substitution for electrophilic addition reaction. [ABSTRACT FROM AUTHOR]

Abstract Copper sulfide (Cu 2 S) microspheres were easily prepared by reducing copper sulphate with ascorbic acid in sodium thiosulfate solution at room temperature and employed copper sulphate and sodium thiosulfate as Cu and S sources, respectively. The as-prepared Cu 2 S microspheres were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties including cyclic voltammetry, galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy were also investigated. The experimental results showed that the as-prepared Cu 2 S microspheres based on the three-electrode test system exhibited a maximum specific capacitance of 444.2 F g−1, and the energy density was up to 25.4 Wh·kg−1 with high power density of 4.1 kW kg−1 at the current density of 1 A g−1. Furthermore, Cu 2 S microspheres also showed outstanding long-term cycling stability with more than 87% capacitance retention over 6000 cycles due to their microspheres structure, which facilitate efficient charge transport and promote electrolyte diffusion. The Cu 2 S-1:1.5 was used as a positive electrode for the fabrication of asymmetric supercapacitor along with reduced GO as the negative electrode, which delivered the high energy density up to 18.6 Wh·kg−1 along with long cycling life and retains up to 89% specific capacitance after 6000 cycles. The excellent results suggest that the Cu 2 S microsphere is a promising candidate as electrode material for high performance supercapacitors. [ABSTRACT FROM AUTHOR]

Recently, copper sulfide (CuS) quite arouses researchers' interest due to its high theoretical capacity and excellent electroconductivity. However, poor cycling stability seriously limited the application in supercapacitors. In addition to the improvement of cycling performance, it is also a challenge to develop electrode materials with energy density. Herein, RGO/CuS composite is prepared successfully by solvothermal reaction methods. By the observation using FESEM and TEM, CuS microstructure displays regular and tiny nanoparticles, which are supported by RGO sheets. After the electrochemical measurements, RGO/CuS composite exhibits a maximum specific capacitance of 946 F g −1 at 10 mV s −1 and 906 F g −1 at 1 A g −1 , respectively. The excellent cycling stability is also achieved and it maintains 89% retention after 5000 cycles at 5 A g −1 . RGO/CuS composite also possesses high energy density of 105.6 W h kg −1 at the power density of 2.5 kW kg −1 , which indicates that RGO/CuS composite has a bright future as electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Engineered oxide nanoparticles (NPs) are widely applied in insulators, catalyzers, paints, cosmetic products, textiles and semiconductors. Their attachment on cell membrane may lead to cytotoxicity. The effects of Al 2 O 3 , Fe 2 O 3 , SiO 2 , TiO 2 and ZnO NPs on membrane integrity and fluidity were studied using giant or small unilamellar vesicles in this study. Al 2 O 3 and SiO 2 NPs disrupted the oppositely charged membrane, indicating the important role of electrostatic attraction. However, Fe 2 O 3 , TiO 2 and ZnO NPs did not cause serious membrane disruption as Al 2 O 3 and SiO 2 NPs. Membrane fluidity was evaluated by the generalized polarity (GP) values of Laurdan fluorescent emission. SiO 2 NPs induce the membrane gelation of both positively and negatively charged membrane. Al 2 O 3 and ZnO NPs induced the gelation of the oppositely charged membrane, but did not cause obvious membrane gelation to the like charged membrane. The phospholipid molecular structural changes after NP exposure were analyzed by Fourier transform infrared (FT-IR) spectroscopy. FT-IR spectra revealed the hydrogen bond formation between NPs and the carbonyl/phosphate groups of phospholipids. Al 2 O 3 and SiO 2 NPs showed strongest evidence of hydrogen bonding on their FT-IR spectra. It was consistent with the microscopic observation and fluorescent data that Al 2 O 3 and SiO 2 NPs caused more serious membrane disruption and gelation. This study on membrane damage provides further knowledge on the cytotoxicity of nanomaterials and the safety of NP application. [ABSTRACT FROM AUTHOR]

Atmospheric fine particulate matter (PM 2.5 ) was collected to investigate its dispersion in simulated lung fluid (SLF) and its interaction with model cell membranes. Organic acids, NH 4 + , SO 4 2 − and NO 3 − were detected in PM 2.5 soluble fraction, and heavy metals were detected from the total mass. The insoluble fraction contained kaolinite, CaCO 3 , aliphatic carbons, aromatic rings, carboxyl and hydroxyl groups reflected by the infrared spectra. Proteins dispersed PM 2.5 in SLF, resulted in smaller hydrodynamic diameter ( d H ) and slower sedimentation rate. Conversely, phospholipids increased d H value and accelerated sedimentation rate. Giant unilamellar vesicles (GUVs) and supported lipid bilayers (SLBs) were used as model cell membranes. PM 2.5 adhered on and disrupted the membrane containing positively-charged lipids but not the membrane containing neutrally- and negatively-charged lipids, which was monitored by microscopy and a quartz crystal microbalance with dissipation (QCM-D). The cationic sites on membrane were necessary for PM 2.5 adhesion, but membrane should be disrupted by the combined action of electrostatic forces and hydrogen bonds between PM 2.5 oxygen containing groups and the lipid phosphate groups. Our results specified the roles of proteins and phospholipids in PM 2.5 dispersion and transport, highly suggested that the health hazard of PM 2.5 was related to the biomolecules in the lung fluid and the particle surface groups. [ABSTRACT FROM AUTHOR]

Cancer is a major killer of human health and predictions for the carcinogenicity of chemicals are of great importance. In this article, predictive models for the carcinogenicity of organic compounds using QSAR methods for rats and mice were developed based on the data from CPDB. The models was developed based on the data of specific target site liver and classified according to sex of rats and mice. Meanwhile, models were also classified according to whether there is a ring in the molecular structure in order to reduce the diversity of molecular structure. Therefore, eight local models were developed in the final. Taking into account the complexity of carcinogenesis and in order to obtain as much information, DRAGON descriptors were selected as the variables used to develop models. Fitting ability, robustness and predictive power of the models were assessed according to the OECD principles. The external predictive coefficients for validation sets of each model were in the range of 0.711–0.906, and for the whole data in each model were all greater than 0.8, which represents that all models have good predictivity. In order to study the mechanism of carcinogenesis, standardized regression coefficients were calculated for all predictor variables. In addition, the effect of animal sex on carcinogenesis was compared and a trend that female showed stronger tolerance for cancerogen than male in both species was appeared. [ABSTRACT FROM AUTHOR]

Due to its prevalent presence, it is critical to clarify the atmospheric fate of acenaphthylene (Ary). In this paper, the reaction mechanism of the gas-phase ozonolysis of Ary was investigated by using quantum chemistry methods. Possible reaction pathways were discussed, and the theoretical results were compared with the available experimental data. The rate constants of the crucial elementary reactions were determined by the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The main products include secondary ozonide, naphthalene-1,8-dicarbaldehyde, 1,8-naphthalic anhydride, oxaacenaphthylene-2-one, 1-naphthaldehyde, 2-hydroxy-1-naphthaldehyde, and α-hydroxyhydroperoxide. The reaction of the unsaturated cyclo-pentafused ring with O3 is the dominant pathway. The overall rate constant of the O 3 addition reaction is 5.31 × 10 − 16 cm 3 molecule − 1 s − 1 at 298 K and 1 atm. The atmospheric lifetime of Ary determined by O 3 is about 0.75 h. This work provides a comprehensive investigation of the ozonolysis of Ary and should help to understand its atmospheric fate. [ABSTRACT FROM AUTHOR]

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have become a serious environmental concern due to their widespread occurrence and dioxin-like toxicities. In this work, the mechanism of the OH-initiated atmospheric oxidation degradation of 9,10-dichlorophenanthrene (9,10-Cl 2 Phe) was investigated by using high-accuracy quantum chemistry calculations. The rate constants of the crucial elementary reactions were determined by the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The theoretical results were compared with the available experimental data. The main oxidation products are a group of ring-retaining and ring-opening compounds including chlorophenanthrols, 9,10-dichlorophenanthrene-3,4-dione, dialdehydes, chlorophenanthrenequinones, nitro-9,10-Cl 2 Phe and epoxides et al. The overall rate constant of the OH addition reaction is 2.35 × 10 − 12 cm 3 molecule − 1 s − 1 at 298 K and 1 atm. The atmospheric lifetime of 9,10-Cl 2 Phe determined by OH radicals is about 5.05 days. This study provides a comprehensive investigation of the OH-initiated oxidation degradation of 9,10-Cl 2 Phe and should contribute to clarifying its atmospheric fate. [ABSTRACT FROM AUTHOR]

The atmospheric oxidation of polycyclic aromatic hydrocarbons (PAHs) can generate toxic derivatives which contribute to the carcinogenic potential of particulate organic matter. In this work, the mechanism of the OH-initiated atmospheric oxidation of fluoranthene (Flu) was investigated by using high-accuracy molecular orbital calculations. All of the possible oxidation pathways were discussed, and the theoretical results were compared with the available experimental observation. The rate constants of the crucial elementary reactions were evaluated by the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The main oxidation products are a range of ring-retaining and ring-opening chemicals containing fluoranthols, fluoranthones, fluoranthenequinones, nitro-fluoranthenes, dialdehydes and epoxides. The overall rate constant of the OH addition reaction is 1.72 × 10 − 11 cm 3 molecule − 1 s − 1 at 298 K and 1 atm. The atmospheric lifetime of Flu determined by OH radicals is about 0.69 days. This work provides a comprehensive investigation of the OH-initiated oxidation of Flu and should help to clarify its atmospheric conversion. [ABSTRACT FROM AUTHOR]

Highlights: [•] OH-initiated degradation of methomyl in atmosphere has been investigated. [•] The rate constant of Z-methomyl is 5.33×10−14 cm3 molecule−1 s−1. [•] The rate constant of E-methomyl is 7.45×10−14 cm3 molecule−1 s−1. [•] Z-methomyl can exist longer than E-methomyl in atmosphere. [ABSTRACT FROM AUTHOR]

Highlights: [•] Quantum chemical methods are employed to study the title reactions. [•] Major products of the title reactions are indicated in this study. [•] The rate constant of title reaction is calculated in the first time. [•] The lifetime of DMP is also determined. [ABSTRACT FROM AUTHOR]

The ozonolysis of 2,3,7,8-tetra-chlorodibenzo-p-dioxin (2,3,7,8-TCDD) is an efficient degradation way in the atmosphere. The ozonolysis process and possible reactions path of Criegee Intermediates with NO and H 2 O are introduced in detail at the method of MPWB1K/6-31+G(d,p)//MPWB1K/6-311+G(3df,2p) level. In ozonolysis, H 2 O is an important source of OH radical formation and initiated the subsequent degradation reaction. The Rice-Ramsperger-Kassel-Marcus (RRKM) theory was applied to calculate rate constants with the temperature ranging from 200 to 600 K. The rate constant of reaction between 2,3,7,8-TCDD and O 3 is 4.80 × 10 −20 cm 3 /(mole·sec) at 298 K and 760 Torr. The atmospheric lifetime of the reaction species was estimated according to rate constants, which is helpful for the atmospheric model study on the degradation and risk assessment of dioxin. [ABSTRACT FROM AUTHOR]

Highlights: [•] Gas-phase formation of PBDD/Fs from 2,4,5-TBP and 3,4-DBP was studied by DFT. [•] Only BPs with bromine at the ortho position are capable of forming PBDDs. [•] The formation of PBDDs dominates over the formation of PBDFs. [•] The meta bromine facilitates the dimerization of BP radicals, whereas the para and ortho ones suppress it. [•] The formation of PBDDs from BPs is easier compared to that of the analogous PCDDs from CPs. [Copyright &y& Elsevier]

Abstract: The bromophenoxy radicals (BPRs) are key intermediate species involved in the formation of polybrominated dibenzo-p-dioxin/dibenzofurans (PBDD/Fs). In this work, the formation of BPRs from the complete series reactions of 19 bromophenol (BP) congeners with H and OH radicals were investigated theoretically by using the density functional theory (DFT) method and the direct dynamics method. The geometries and frequencies of the reactants, transition states, and products were calculated at the MPWB1K/6-31+G(d,p) level, and the energetic parameters were further refined by the MPWB1K/6-311+G(3df,2p) method. The rate constants were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution over a wide temperature range of 600–1200K. The present study indicates that the reactivity of the O–H bonds in BPs as well as the formation potential of BPRs from BPs is strongly related to the bromine substitution pattern. The obtained results can be used for future estimates of PBDD/F emissions quantity based on the well estimated PCDD/F inventory. [Copyright &y& Elsevier]

Abstract: The reaction mechanisms of vinyl acetate with O3 are investigated by performing Density Functional Theory (DFT) calculations as an attempt to investigate the photooxidation reaction of acetate in the atmosphere. The detailed reaction mechanisms are proposed. The potential energy surface profiles (PESs) are constructed. Several products (formaldehyde, heroperoxymethyl formate and formic acetic anhydride) resulting from the gas phase reactions are identified by comparing with the experimental results. The experimentally uncertain dominant product of CH2OO is confirmed to be heroperoxymethyl formate. The experimentally unknown mechanism for the formation of formic acetic anhydride from CH3OCHOO is proposed. Rate constants of the reaction over the temperature range of 200–2000K are obtained by using Rice–Ramsperger–Kassel–Marcus (RRKM) theory based on the above PES calculations. The rate constants are independent on pressure. [Copyright &y& Elsevier]

Abstract: Trichlorfon [O,O-dimethyl-(2,2,2-trichloro-1-hydroxy-ethyl) phosphonate] (TCF) is a kind of widely used organophosphorus pesticides. In this paper, the mechanism and possible oxidation products for the OH-initiated reactions of TCF are studied at the MPWB1K/6–311+G(3df,2p)//MPWB1K/6–31+G(d,p) level. The study shows that H abstraction reaction from the CH3 group and the CH group as well as OH addition reaction to the P atom are energetically favorable for the reactions of TCF and the main products are (CH3O)2POOH (P1), CCl3CHOHPOOH(OCH3) (P2), CH3OPO2 (P3), CCl3COPO(OCH3)2 (P6) and HCHO. On the basis of the quantum chemical information, the kinetic calculation is performed and the rate constants are calculated over a temperature range of 200–800K using the transition state theory and canonical variational transition state theory with small-curvature tunneling effect. The Arrhenius formulas of rate constants with the temperature are fitted and the lifetimes of the reaction species in the troposphere are estimated according to the rate constants, which can provide helpful information for the model simulation study. [Copyright &y& Elsevier]

Abstract: The ocimene ozonolysis reaction is one of the most important processes for the formation of secondary organic aerosol (SOA). In this paper, molecular orbital theory has been performed for the reaction of ocimene with O3, and the detailed reaction mechanisms of active intermediates with H2O or NO are also presented. The geometry parameters and vibrational frequencies of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis set. Single-point energy calculations are carried out at the MPWB1K/6-311+G(3df,2p) level. On the basis of the quantum chemical information, the Rice–Ramsperger–Kassel–Marcus (RRKM) theory and the canonical variational transition state theory (CVT) with small-curvature tunneling effect (SCT) are used to calculate the rate constants over the temperature range of 200–800 K. The arrhenius formulas of rate constants with the temperature are fitted, which can provide helpful information for the model simulation study. The atmospheric lifetimes of the reaction species are estimated according to the rate constants. [Copyright &y& Elsevier]

Abstract: Diazinon is a member of the organophosphorus class of insecticides. It has been regarded as an important atmospheric pollutant because of its high detection-frequency in the air and potential adverse effects on humans and wildlife. In this paper, the reaction mechanism and possible degradation products for the OH-initiated atmospheric degradation of diazinon were investigated and the rate constants of crucial elementary steps over the temperature range of 180–370 K were predicted. Present results show that OH addition to C4 atom in the pyrimidyl ring, H abstraction from the –CH– moiety as well as OH addition to P atom are the dominant pathways for the reaction of diazinon with OH radicals. The dominant degradation products are diazoxon, SO2, P3, CH3CHO, P4, CH3CO, P14 as well as CH3CHCH3. This work provides a comprehensive investigation of the OH-initiated atmospheric degradation of diazinon and should help to clarify its potential risk to non-targets. [Copyright &y& Elsevier]