Decreased Human Respiratory Absorption Factors of Aromatic Hydrocarbons at Lower Exposure Levels: The Dual Effect in Reducing Ambient Air Toxics

Respiratory absorption factors (AFs) are important parameters for assessing human health risks of long-term inhalation exposure to low-level hazardous air pollutants. However, it is uncertain whether previously measured respiratory AFs for high-level exposures could be directly applied. Here we measured real-time respiratory AFs using proton transfer reaction time-of-flight mass spectrometry for 50 subjects (20–30 years of age; 24 females and 26 males) exposed in a normal office room with aromatic hydrocarbons (AHs) at concentrations of several parts per billion by volume. The mean respiratory AFs of benzene, toluene, and C8-aromatics (ethylbenzene and xylenes) from all subjects were 28.2, 63.3, and 66.6%, respectively. No gender difference in the respiratory AFs of AHs was observed. Correlation analysis revealed that exposure concentration, rather than physiological parameters like body mass index or body fat ratio, was the dominant factor influencing the AFs of AHs. The results also demonstrated that respiratory AFs decreased in a logarithmic way when exposure levels of AHs were decreased. The decreased respiratory AFs at lowered exposure levels suggest the dual effect of reducing ambient air toxics like AHs with a decrease in human inhalation intake

1-D wave-like chain, twofold 2-D layer, and chiral 3-D open framework based on multidentate ligand: structural diversities, thermal properties, and photoluminescence

<p>From 1-D to 3-D zinc coordination polymers based on multifunctional flexible 4-(1,2,4-triazole-methylene)-benzonitrile (tzbt), {[Zn(tzbt)₂(bdc)]·2H₂O}_n (<b>1</b>), [Zn(tzbc)₂]_n (<b>2</b>), and [Zn(bpdc)(H₂O)]_n (<b>3</b>) (bdc = 1,4-benzenedicarboxylic acid, tzbc = 4-(1,2,4-triazole-methylene)-benzoic acid, bpdc = 4,4′-biphenyldicarboxylic acid), were synthesized under hydrothermal conditions. The tzbt was synthesized by <i>N</i>-alkylation and hydrolyzed <i>in situ</i> to produce tzbc (in <b>2</b>). Single-crystal X-ray diffraction analysis reveals that <b>1</b> displays 1-D wave-like chains based on [Zn(bdc)]_n. <b>2</b> is a chiral twofold interpenetrating 2-D architecture constructed with “V”-shaped tzbc. <b>3</b> is a 3-D chiral compound constructed from achiral H₂bpdc with right-handed helical chains. <b>1–3</b> display stable blue-emitting luminescence with emission maxima ranging from 383 to 410 nm, depending on ligand-centered <i>π</i>*→<i>π</i> transitions. The effects of different polarity solvents and temperature on luminescence are discussed. TGA and VT-XPRD reveal that <b>2</b> has thermal stability to 360 °C.</p

(<i>E</i>)‑<i>N</i>‑(Pyridine-2-ylmethylene)arylamine as an Assembling Ligand for Zn(II)/Cd(II) Complexes: Aryl Substitution and Anion Effects on the Dimensionality and Luminescence Properties of the Supramolecular Metal–Organic Frameworks

Using five Schiff base ligands (<i>E</i>)-<i>N</i>-(pyridine-2-yl) (CHNPhR) (where R = 4–CH₃, <b>L</b>^<b>1</b>; 2,6-(CH₃)₂, <b>L</b>^<b>2</b>; 2,4,6-(CH₃)₃, <b>L</b>^<b>3</b>; 2,6-(C₂H₅)₂, <b>L</b>^<b>4</b>; 2,6-(<i>i</i>-C₃H₇)₂, <b>L</b>^<b>5</b>), nine Zn­(II)/Cd­(II) complexes, namely, <b>Zn1</b>–<b>Zn3</b>, <b>Cd1</b>, <b>Cd2</b>, <b>Cd3a</b>, <b>Cd3b</b>, <b>Cd4</b>, and <b>Cd5</b>, have been successfully synthesized. The structures of the Zn­(II)/Cd­(II) complexes have been established by single crystal X-ray diffraction and further physically characterized by ¹H NMR, FT–IR, and elemental analysis. The crystal structures of these complexes indicate that the structures of ligand and anions can directly influence the formation of 1D → 3D supramolecular metal–organic frameworks (SMOFs) via C–H<b>···</b>O/C–H<b>···</b>Cl hydrogen bonds and π<b>···</b>π interactions. Upon irradiation with UV light, the nine Zn­(II)/Cd­(II) complexes display deep blue emissions of 401–436 nm in acetonitrile solution and light blue or bluish green emissions of 485–575 nm in the solid state, respectively. The photoluminescence properties of nine Zn­(II)/Cd­(II) complexes can be finely and predictably tuned over a wide range of wavelengths by small and easily implemented changes to ligand structure. It is worth noting that <b>Zn1</b> and <b>Cd1</b> exhibit obvious aggregation-induced emission enhancement (AIEE) properties in the CH₃CN–H₂O mixture solutions

Semivolatile Organic Compounds (SOCs) in Fine Particulate Matter (PM_2.5) during Clear, Fog, and Haze Episodes in Winter in Beijing, China

Few efforts have been made to elucidate the influence of weather conditions on the fate of semivolatile organic compounds (SOCs). Here, daily fine particulate matter (PM_2.5) during clear, haze, and fog episodes collected in the winter in Beijing, China was analyzed for polycyclic aromatic hydrocarbons (PAHs), brominated flame retardants (BFRs), and organophosphate flame retardants (OPFRs). The total concentrations of PAHs, OPFRs, and BFRs had medians of 45.1 ng/m³ and 1347 and 46.7 pg/m³, respectively. The temporal pattern for PAH concentrations was largely dependent on coal combustion for residential heating. OPFR compositions that change during colder period were related to enhanced indoor emissions due to heating. The mean concentrations of SOCs during haze and fog days were 2–10 times higher than those during clear days. We found that BFRs with lower octanol and air partition coefficients tended to increase during haze and fog episodes, be removed from PM_2.5 during clear episodes, or both. For PAHs and OPFRs, pollutants that are more recalcitrant to degradation were prone to accumulate during haze and fog days. The potential source contribution function (PSCF) model indicated that southern and eastern cities were major source regions of SOCs at this site

Tunable Luminescence and Application in Dye-Sensitized Solar Cells of Zn(II)/Hg(II) Complexes: Methyl Substitution-Induced Supramolecular Structures Based on (<i>E</i>)‑<i>N</i>‑(6-Methoxypyridin-2-ylmethylene)arylamine Derivatives

Using Schiff-base ligands (<i>E</i>)-<i>N</i>-(6-methoxypyridin-2-yl)­(CHNAr) (where Ar = C₆H₅, <b>L</b>_<b>1</b>; 2-MeC₆H₄, <b>L</b>_<b>2</b>; 2,4,6-Me₃C₆H₂, <b>L</b>_<b>3</b>), six Zn­(II)/Hg­(II) complexes, namely, [Zn<b>L</b>_<b>1</b>Cl₂] (<b>Zn1</b>), [Hg<b>L</b>_<b>1</b>Cl₂] (<b>Hg1</b>), [Zn<b>L</b>_<b>2</b>Cl₂] (<b>Zn2</b>), [Hg<b>L</b>_<b>2</b>Cl₂] (<b>Hg2</b>), [Zn<b>L</b>_<b>3</b>Cl₂] (<b>Zn3</b>), and [Hg<b>L</b>_<b>3</b>Cl₂] (<b>Hg3</b>) have been synthesized under solvothermal conditions. The structures of six complexes have been established by X-ray single-crystal analysis and further physically characterized by EA, FT-IR, ¹H NMR, and ESI-MS. The crystal structures of these complexes indicate that noncovalent interactions, such as hydrogen bonds, C–H···Cl, and π<b>···</b>π stacking, play essential roles in constructing the resulting supramolecular structures (1D for <b>Hg3</b>; 2D for <b>Zn2</b>, <b>Hg2</b>; 3D for <b>Zn1</b>, <b>Hg1</b>, and <b>Zn3</b>). Upon irradiation with UV light, the emission of complexes <b>Zn1</b>–<b>Zn3</b> and <b>Hg1</b>–<b>Hg3</b> could be finely tuned from green (480–540 nm) in the solid state to blue (402–425 nm) in acetonitrile solution. It showed that the ligand and metal cation can influence the structures and luminescence properties of complexes such as emission intensities and maximum wavelengths. Since these ligands and complexes could compensate for the absorption of N719 in the low-wavelength region of the visible spectrum and reduce charge recombination of the injected electron, the ligands <b>L</b>_<b>1</b>–<b>L</b>_<b>3</b> and complexes <b>Zn3</b>/<b>Hg3</b> were employed to prepare cosensitized dye-sensitized solar cells devices for investigating the influences of the electron-donating group and coordination on the DSSCs performance. Compared to DSSCs only being sensitized by N719, these prepared ligands and complexes chosen to cosensitize N719 in solar cell do enhanced its performance by 11–41%. In particular, a DSSC using <b>L</b>_<b>3</b> as cosensitizer displays better photovoltaic performance with a short circuit current density of 18.18 mA cm^–2, corresponding to a conversion efficiency of 7.25%. It is much higher than that for DSSCs only sensitized by N719 (5.14%)

Tunable Luminescence and Application in Dye-Sensitized Solar Cells of Zn(II)/Hg(II) Complexes: Methyl Substitution-Induced Supramolecular Structures Based on (<i>E</i>)‑<i>N</i>‑(6-Methoxypyridin-2-ylmethylene)arylamine Derivatives

Using Schiff-base ligands (<i>E</i>)-<i>N</i>-(6-methoxypyridin-2-yl)­(CHNAr) (where Ar = C₆H₅, <b>L</b>_<b>1</b>; 2-MeC₆H₄, <b>L</b>_<b>2</b>; 2,4,6-Me₃C₆H₂, <b>L</b>_<b>3</b>), six Zn­(II)/Hg­(II) complexes, namely, [Zn<b>L</b>_<b>1</b>Cl₂] (<b>Zn1</b>), [Hg<b>L</b>_<b>1</b>Cl₂] (<b>Hg1</b>), [Zn<b>L</b>_<b>2</b>Cl₂] (<b>Zn2</b>), [Hg<b>L</b>_<b>2</b>Cl₂] (<b>Hg2</b>), [Zn<b>L</b>_<b>3</b>Cl₂] (<b>Zn3</b>), and [Hg<b>L</b>_<b>3</b>Cl₂] (<b>Hg3</b>) have been synthesized under solvothermal conditions. The structures of six complexes have been established by X-ray single-crystal analysis and further physically characterized by EA, FT-IR, ¹H NMR, and ESI-MS. The crystal structures of these complexes indicate that noncovalent interactions, such as hydrogen bonds, C–H···Cl, and π<b>···</b>π stacking, play essential roles in constructing the resulting supramolecular structures (1D for <b>Hg3</b>; 2D for <b>Zn2</b>, <b>Hg2</b>; 3D for <b>Zn1</b>, <b>Hg1</b>, and <b>Zn3</b>). Upon irradiation with UV light, the emission of complexes <b>Zn1</b>–<b>Zn3</b> and <b>Hg1</b>–<b>Hg3</b> could be finely tuned from green (480–540 nm) in the solid state to blue (402–425 nm) in acetonitrile solution. It showed that the ligand and metal cation can influence the structures and luminescence properties of complexes such as emission intensities and maximum wavelengths. Since these ligands and complexes could compensate for the absorption of N719 in the low-wavelength region of the visible spectrum and reduce charge recombination of the injected electron, the ligands <b>L</b>_<b>1</b>–<b>L</b>_<b>3</b> and complexes <b>Zn3</b>/<b>Hg3</b> were employed to prepare cosensitized dye-sensitized solar cells devices for investigating the influences of the electron-donating group and coordination on the DSSCs performance. Compared to DSSCs only being sensitized by N719, these prepared ligands and complexes chosen to cosensitize N719 in solar cell do enhanced its performance by 11–41%. In particular, a DSSC using <b>L</b>_<b>3</b> as cosensitizer displays better photovoltaic performance with a short circuit current density of 18.18 mA cm^–2, corresponding to a conversion efficiency of 7.25%. It is much higher than that for DSSCs only sensitized by N719 (5.14%)

Organosulfates from Pinene and Isoprene over the Pearl River Delta, South China: Seasonal Variation and Implication in Formation Mechanisms

Biogenic organosulfates (OSs) are important markers of secondary organic aerosol (SOA) formation involving cross reactions of biogenic precursors (terpenoids) with anthropogenic pollutants. Until now, there has been rare information about biogenic OSs in the air of highly polluted areas. In this study, fine particle (PM_2.5) samples were separately collected in daytime and nighttime from summer to fall 2010 at a site in the central Pearl River Delta (PRD), South China. Pinene-derived nitrooxy-organosulfates (pNOSs) and isoprene-derived OSs (iOSs) were quantified using a liquid chromatograph (LC) coupled with a tandem mass spectrometer (MS/MS) operated in negative electrospray ionization (ESI) mode. The pNOSs with MW 295 exhibited higher levels in fall (151 ± 86.9 ng m^–3) than summer (52.4 ± 34.0 ng m^–3), probably owing to the elevated levels of NOx and sulfate in fall when air masses mainly passed through city clusters in the PRD and biomass burning was enhanced. In contrast to observations elsewhere where higher levels occurred at nighttime, pNOS levels in the PRD were higher during the daytime in both seasons, indicating that pNOS formation was likely driven by photochemistry over the PRD. This conclusion is supported by several lines of evidence: the specific pNOS which could be formed through both daytime photochemistry and nighttime NO₃ chemistry exhibited no day–night variation in abundance relative to other pNOS isomers; the production of the hydroxynitrate that is the key precursor for this specific pNOS was found to be significant through photochemistry but negligible through NO₃ chemistry based on the mechanisms in the Master Chemical Mechanism (MCM). For iOSs, 2-methyltetrol sulfate ester which could be formed from isoprene-derived epoxydiols (IEPOX) under low-NOx conditions showed low concentrations (below the detection limit to 2.09 ng m^–3), largely due to the depression of IEPOX formation by the high NOx levels over the PRD