We report a 2-family cluster of persons infected with severe acute respiratory syndrome coronavirus 2 in the city of Zhoushan, Zhejiang Province, China, during January 2020. The infections resulted ...from contact with an infected but potentially presymptomatic traveler from the city of Wuhan in Hubei Province.
Broadening the optical absorption of organic photovoltaic (OPV) materials by enhancing the intramolecular push-pull effect is a general and effective method to improve the power conversion ...efficiencies of OPV cells. However, in terms of the electron acceptors, the most common molecular design strategy of halogenation usually results in down-shifted molecular energy levels, thereby leading to decreased open-circuit voltages in the devices. Herein, we report a chlorinated non-fullerene acceptor, which exhibits an extended optical absorption and meanwhile displays a higher voltage than its fluorinated counterpart in the devices. This unexpected phenomenon can be ascribed to the reduced non-radiative energy loss (0.206 eV). Due to the simultaneously improved short-circuit current density and open-circuit voltage, a high efficiency of 16.5% is achieved. This study demonstrates that finely tuning the OPV materials to reduce the bandgap-voltage offset has great potential for boosting the efficiency.
2D MXene, Ti3C2 (TC), has displayed enormous potential in applications in photothermal therapy (PTT), attributing to its biocompatibility and outstanding photothermal conversion capability. However, ...some tumor ablations are difficult to be realized completely by monotherapy due to the essential defects of monotherapy and intricate tumor microenvironment (TME). In this work, the appropriate doped Fe2+ ions are anchored into the layers of 2D ultrathin TC nanosheets (TC NSs) to synthesize a novel multifunctional nanoshell of Fe(II)‐Ti3C2 (FTC) through interlayer electrostatic adsorption. FTC possesses superior photothermal conversion efficiency (PTCE) than TC NSs, attributing to the enhanced conductivity promoted by interlaminar ferrous ion‐channels. Moreover, Fenton reaction based on ferrous ions endows FTC the abilities of reactive oxide species (ROS) releasing and glutathione (GSH) suppression triggered by near‐infrared (NIR) laser, featuring splendid biocompatibility and curative effect in hypoxic TME. Meanwhile, magnetic resonance imaging (MRI) responding in FTC reveals the potential as an integrated diagnosis and treatment nanoplatform. FTC could provide new insights into the development of multimoded synergistic nanoplatform for biological applications, especially breaking the shackles of MXenes merely used as a photo‐thermal agent (PTA), adopting it to bioimaging sensor and drug loading.
Near‐infrared (NIR) activated multimodal nanoplatform Fe‐Ti3C2 (FTC) is developed by electrostatic adsorption between Ti3C2 and Fe(II). FTC can generate reactive oxygen species (ROS) and suppress glutathione (GSH) under NIR excitation. FTC has the superior photothermal performance than Ti3C2. The ferrous ions also endow FTC the ability to serve as a T1 and T2 dual‐responding magnetic resonance contrast agent.
Transition metal‐based nitrogen‐doped carbon (M‐Nx‐C) is considered as a promising catalyst for the oxygen reduction reaction (ORR) in clean energy storage and conversion devices. Herein, ZnCo ...dual‐atomic sites are incorporated in hierarchical N‐doped carbon (HNC), with 1D nanotubes wrapped in 2D nanosheets structure (termed as 1D@2D ZnCo‐HNC), via a one‐step bio‐inspired pyrolysis. The feeding ratio of Zn to Co precursor and pyrolytic temperature are critically modulated to achieve well‐defined morphologies of the products, endowing them with the integrated merits of nanotubes and nanosheets as efficient ORR catalysts. Benefiting from the particular structure and electronic regulation of Zn on Co, the ZnCo‐Nx dual‐atomic system exhibits excellent ORR catalytic characteristics with an onset potential of 1.05 V and a half‐wave potential of 0.82 V. Density functional theory calculations further explain the regulating role of Zn, such that the adjusted Co in ZnCo‐Nx sites significantly reduces the energy cost to ultimately facilitate the ORR. Moreover, the Zn–air battery assembled with ZnCo‐HNC is capable of delivering the maximum power density of 123.7 mW cm−2 and robust stability for 110 h (330 cycles). This method provides a promising strategy for fabricating efficient transition metal‐based carbon catalysts for green energy devices.
With the unique 1D@2D structure and abundant ZnCo dual‐atomic sites, bio‐inspired ZnCo‐HNC exhibits excellent catalytic performances for the oxygen reduction reaction and a home‐assembled Zn–air battery. Density functional theory calculations further demonstrate that Co is the main active center in the ZnCo‐Nx system, while Zn serves as the charge adjuster.
We report an asymptomatic child who was positive for a coronavirus by reverse transcription PCR in a stool specimen 17 days after the last virus exposure. The child was virus positive in stool ...specimens for at least an additional 9 days. Respiratory tract specimens were negative by reverse transcription PCR.
Decreasing the energy loss is one of the most feasible ways to improve the efficiencies of organic photovoltaic (OPV) cells. Recent studies have suggested that non‐radiative energy loss (Enon-radloss
...) is the dominant factor that hinders further improvements in state‐of‐the‐art OPV cells. However, there is no rational molecular design strategy for OPV materials with suppressed Enon-radloss
. Herein, taking molecular surface electrostatic potential (ESP) as a quantitative parameter, we establish a general relationship between chemical structure and intermolecular interactions. The results reveal that increasing the ESP difference between donor and acceptor will enhance the intermolecular interaction. In the OPV cells, the enhanced intermolecular interaction will increase the charge‐transfer (CT) state ratio in its hybridization with the local exciton state to facilitate charge generation, but simultaneously result in a larger Enon-radloss
. These results suggest that finely tuning the ESP of OPV materials is a feasible method to further improve the efficiencies of OPV cells.
Non‐radiative energy loss in organic photovoltaic cells can be achieved by tuning the charge‐transfer state ratio in the hybridized state with the local exciton state. The molecular electrostatic potential (ESP) is considered as a quantitative parameter. By adjusting the ESP difference between PBDB‐TF and BTP‐XF, non‐radiative energy loss is reduced from 0.23 to 0.15 eV.
A cluster of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infections was found in a cargo ship under repair in Zhoushan, China. Twelve of 20 crew members were identified as SARS‐CoV‐2 ...positive. We analyzed four sequences and identified them all in the Delta branch emerging from India with 7–8 amino acid mutation sites in the spike protein.
Foundering of mafic lower continental crust into underlying convecting mantle has been proposed as one means to explain the unusually evolved chemical composition of Earth's continental crust, yet ...direct evidence of this process has been scarce. Here we report that Late Jurassic high-magnesium andesites, dacites and adakites (siliceous lavas with high strontium and low heavy-rare-earth element and yttrium contents) from the North China craton have chemical and petrographic features consistent with their origin as partial melts of eclogite that subsequently interacted with mantle peridotite. Similar features observed in adakites and some Archaean sodium-rich granitoids of the tonalite-trondhjemite-granodiorite series have been interpreted to result from interaction of slab melts with the mantle wedge. Unlike their arc-related counterparts, however, the Chinese magmas carry inherited Archaean zircons and have neodymium and strontium isotopic compositions overlapping those of eclogite xenoliths derived from the lower crust of the North China craton. Such features cannot be produced by crustal assimilation of slab melts, given the high Mg#, nickel and chromium contents of the lavas. We infer that the Chinese lavas derive from ancient mafic lower crust that foundered into the convecting mantle and subsequently melted and interacted with peridotite. We suggest that lower crustal foundering occurred within the North China craton during the Late Jurassic, and thus provides constraints on the timing of lithosphere removal beneath the North China craton.
Optimizing the molecular structures of organic photovoltaic (OPV) materials is one of the most effective methods to boost power conversion efficiencies (PCEs). For an excellent molecular system with ...a certain conjugated skeleton, fine tuning the alky chains is of considerable significance to fully explore its photovoltaic potential. In this work, the optimization of alkyl chains is performed on a chlorinated nonfullerene acceptor (NFA) named BTP‐4Cl‐BO (a Y6 derivative) and very impressive photovoltaic parameters in OPV cells are obtained. To get more ordered intermolecular packing, the n‐undecyl is shortened at the edge of BTP‐eC11 to n‐nonyl and n‐heptyl. As a result, the NFAs of BTP‐eC9 and BTP‐eC7 are synthesized. The BTP‐eC7 shows relatively poor solubility and thus limits its application in device fabrication. Fortunately, the BTP‐eC9 possesses good solubility and, at the same time, enhanced electron transport property than BTP‐eC11. Significantly, due to the simultaneously enhanced short‐circuit current density and fill factor, the BTP‐eC9‐based single‐junction OPV cells record a maximum PCE of 17.8% and get a certified value of 17.3%. These results demonstrate that minimizing the alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.
By finely optimizing the alkyl chains, the nonfullerene acceptor named BTP‐eC9 is synthesized and a maximum power conversion efficiency of 17.8% in organic photovoltaic cells is recorded. This work demonstrates that the optimization of alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving photovoltaic performance.
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