End-Capping Effect of Quinoxalino[2,3‑<i>b</i>′]porphyrin on Donor–Acceptor Copolymer and Improved Performance of Polymer Solar Cells

A series of end-capped donor–acceptor copolymers, P­(BT-DPP)-T, P­(BT-DPP)-QP, and P­(BT-DPP)-QPZn, were synthesized by Stille coupling of 2,2′-bithiophene (BT) and diketopyrrolopyrrole (DPP) with end-caps of thiophene (T), quinoxalino­[2,3-<i>b</i>′]­porphyrin (QP), and quinoxalino­[2,3-<i>b</i>′]­porphyrinatozinc (QPZn), respectively. Compared with the counterpart, P­(BT-DPP), which contains no end-caps, P­(BT-DPP)-QP and P­(BT-DPP)-QPZn showed remarkably enhancement of light absorption in the range of <i>ca</i>. 400–550 nm resulted from the end-capping effect of porphyrins. Bulk heterojunction polymer solar cells (PSCs) based on these polymers were fabricated and the results showed significant improvement of power conversion efficiencies (PCEs) of the end-capped polymers. Especially, ligand addivie, 4,4′-bipyridine (Bipy), was applied to the PSCs based on polymers end-capped by porphyrins and the PCE of the photovoltaic device based on P­(BT-DPP)-QPZn significantly improved from 2.92% to 4.45% with the comprehensive benefits of optimization strategies such as using additives and thermal annealing. Furthermore, thermal aging experiments showed increased stability of the optimal morphology of P­(BT-DPP)-QPZn:PC₇₁BM blend film after the use of Bipy. This study provides a promising strategy to design donor–acceptor copolymers with multifunctional end-caps and to use ligand additives for achieving PSCs with both high-efficiency and long-term stability, which are critical for the devices to be commercially useful

Assessment of the Air–Soil Partitioning of Polycyclic Aromatic Hydrocarbons in a Paddy Field Using a Modified Fugacity Sampler

Rice, one of the most widely cultivated crops, has received great attention in contaminant uptake from soil and air, especially for the special approaches used for its cultivation. The dry–wet alternation method can influence the air–soil partitioning of semivolatile organic compounds (SVOCs) in the paddy ecosystem. Here, we modified a fugacity sampler to investigate the air–surface in situ partitioning of ubiquitous polycyclic aromatic hydrocarbons (PAHs) at different growth stages in a suburban paddy field in South China. The canopy of rice can form a closed space, which acts like a chamber that can force the air under the canopy to equilibrate with the field surface. When we compared the fugacities calculated using a fugacity model of the partition coefficients to the measured fugacities, we observed similar trends in the variation, but significantly different values between different growing stages, especially during the flooding stages. However, the measured and calculated fugacity fractions were comparable when uncertainties in our calculations were considered, with the exception of the high molecular weight (HMW) PAHs. The measured fugacity fractions suggested that the HMW PAHs were also closed to equilibrium between the paddy field and atmosphere. The modified fugacity sampler provided a novel way of accurately determining the in situ air–soil partitioning of SVOCs in a wet paddy field

Organochlorine Pesticides in the Atmosphere and Surface Water from the Equatorial Indian Ocean: Enantiomeric Signatures, Sources, and Fate

Nineteen pairs of gaseous and surface seawater samples were collected along the cruise from Malaysia to the south of Bay of Bengal passing by Sri Lanka between April 12 and May 4, 2011 on the Chinese research vessel Shiyan I to investigate the latest OCP pollution status over the equatorial Indian Ocean. Significant decrease of α-HCH and γ-HCH was found in the air and dissolved water phase owing to global restriction for decades. Substantially high levels of <i>p,p</i>′-DDT, <i>o,p</i>′-DDT, trans-chlordane (TC), and cis-chlordane (CC) were observed in the water samples collected near Sri Lanka, indicating fresh continental riverine input of these compounds. Fugacity fractions suggest equilibrium of α-HCH at most sampling sites, while net volatilization for DDT isomers, TC and CC in most cases. Enantiomer fractions (EFs) of α-HCH and <i>o,p</i>′-DDT in the air and water samples were determined to trace the source of these compounds in the air. Racemic or close to racemic composition was found for atmospheric α-HCH and <i>o,p</i>′-DDT, while significant depletion of (+) enantiomer was found in the water phase, especially for <i>o,p</i>′-DDT (EFs = 0.310 ± 0.178). 24% of α-HCH in the lower air over the open sea of the equatorial Indian Ocean is estimated to be volatilized from local seawater, indicating that long-range transport is the main source

Source Apportionment Using Radiocarbon and Organic Tracers for PM_2.5 Carbonaceous Aerosols in Guangzhou, South China: Contrasting Local- and Regional-Scale Haze Events

We conducted a source apportionment and investigated the atmospheric behavior of carbonaceous aerosols during hazy and normal days using radiocarbon (¹⁴C) and biomass burning/secondary organic aerosol (SOA) tracers during winter in Guangzhou, China. Haze episodes were formed either abruptly by local emissions or through the accumulation of particles transported from other areas. The average contributions of fossil carbon to elemental carbon (EC), water-insoluble organic carbon, and water-soluble organic carbon were 71 ± 10%, 40 ± 6% and 33 ± 3%, respectively. High contributions of fossil carbon to EC (80–90%) were observed for haze samples that were substantially impacted by local emissions, as were the highest (lowest) ratios for NO₃^–/SO₄^2– (OC/EC), which indicates that these particles mainly came from local vehicle exhaust. Low contributions of fossil carbon to EC (60–70%) were found for haze particles impacted by regional transport. Secondary organic carbon (SOC) calculated using SOA tracers accounts for only ∼20% of the SOC estimated by ¹⁴C, which is probably because some important volatile organic carbons are not taken into account in the SOA tracer calculation method and because of the large discrepancy in ambient conditions between the atmosphere and smog chambers. A total of 33 ± 11% of the SOC was of fossil origin, a portion of which could be influenced by humidity