Feng Gao

Fullerene‐Free Polymer Solar Cells with over 11% Efficiency and Excellent Thermal Stability

A nonfullerene-based polymer solar cell (PSC) that significantly outperforms fullerene-based PSCs with respect to the power-conversion efficiency is demonstrated for the first time. An efficiency of >11%, which is among the top values in the PSC field, and excellent thermal stability is obtained using PBDB-T and ITIC as donor and acceptor, respectively.

Preparation and photoabsorption characterization of BiFeO3 nanowires

Perovskite-type polycrystalline BiFeO3 (BFO) nanowires (∼50nm in diameter and ∼5μm in length) were synthesized using the anodized alumina template technique. An energy band gap of ∼2.5eV was determined from the UV-visible diffuse reflectance spectrum, and its photocatalytic ability to produce O2 was revealed under UV irradiation. Weak ferromagnetism at room temperature and superparamagnetism at low temperature were observed for the BFO nanowires, different from the antiferromagnetic order in bulk BFO, reflecting the significant size effects on the magnetic ordering of BFO.

Streptococcal Toxic Shock Syndrome Caused by Streptococcus suis Serotype 2

Background Streptococcus suis serotype 2 ( S. suis 2, SS2) is a major zoonotic pathogen that causes only sporadic cases of meningitis and sepsis in humans. Most if not all cases of Streptococcal toxic shock syndrome (STSS) that have been well-documented to date were associated with the non-SS2 group A streptococcus (GAS). However, a recent large-scale outbreak of SS2 in Sichuan Province, China, appeared to be caused by more invasive deep-tissue infection with STSS, characterized by acute high fever, vascular collapse, hypotension, shock, and multiple organ failure. Methods and Findings We investigated this outbreak of SS2 infections in both human and pigs, which took place from July to August, 2005, through clinical observation and laboratory experiments. Clinical and pathological characterization of the human patients revealed the hallmarks of typical STSS, which to date had only been associated with GAS infection. Retrospectively, we found that this outbreak was very similar to an earlier outbreak in Jiangsu Province, China, in 1998. We isolated and analyzed 37 bacterial strains from human specimens and eight from pig specimens of the recent outbreak, as well as three human isolates and two pig isolates from the 1998 outbreak we had kept in our laboratory. The bacterial isolates were examined using light microscopy observation, pig infection experiments, multiplex-PCR assay, as well as restriction fragment length polymorphisms (RFLP) and multiple sequence alignment analyses. Multiple lines of evidence confirmed that highly virulent strains of SS2 were the causative agents of both outbreaks. Conclusions We report, to our knowledge for the first time, two outbreaks of STSS caused by SS2, a non-GAS streptococcus. The 2005 outbreak was associated with 38 deaths out of 204 documented human cases; the 1998 outbreak with 14 deaths out of 25 reported human cases. Most of the fatal cases were characterized by STSS; some of them by meningitis or severe septicemia. The molecular mechanisms underlying these human STSS outbreaks in human beings remain unclear and an objective for further study.

Molecular basis of binding between novel human coronavirus MERS-CoV and its receptor CD26

The newly emergent Middle East respiratory syndrome coronavirus (MERS-CoV) can cause severe pulmonary disease in humans, representing the second example of a highly pathogenic coronavirus, the first being SARS-CoV. CD26 (also known as dipeptidyl peptidase 4, DPP4) was recently identified as the cellular receptor for MERS-CoV. The engagement of the MERS-CoV spike protein with CD26 mediates viral attachment to host cells and virus–cell fusion, thereby initiating infection. Here we delineate the molecular basis of this specific interaction by presenting the first crystal structures of both the free receptor binding domain (RBD) of the MERS-CoV spike protein and its complex with CD26. Furthermore, binding between the RBD and CD26 is measured using real-time surface plasmon resonance with a dissociation constant of 16.7 nM. The viral RBD is composed of a core subdomain homologous to that of the SARS-CoV spike protein, and a unique strand-dominated external receptor binding motif that recognizes blades IV and V of the CD26 β-propeller. The atomic details at the interface between the two binding entities reveal a surprising protein–protein contact mediated mainly by hydrophilic residues. Sequence alignment indicates, among betacoronaviruses, a possible structural conservation for the region homologous to the MERS-CoV RBD core, but a high variation in the external receptor binding motif region for virus-specific pathogenesis such as receptor recognition.

Highly Efficient Perovskite Nanocrystal Light‐Emitting Diodes Enabled by a Universal Crosslinking Method

The preparation of highly efficient perovskite nanocrystal light-emitting diodes is shown. A new trimethylaluminum vapor-based crosslinking method to render the nanocrystal films insoluble is applied. The resulting near-complete nanocrystal film coverage, coupled with the natural confinement of injected charges within the perovskite crystals, facilitates electron-hole capture and give rise to a remarkable electroluminescence yield of 5.7%.

Mapping Polymer Donors toward High-Efficiency Fullerene Free Organic Solar Cells.

Five polymer donors with distinct chemical structures and different electronic properties are surveyed in a planar and narrow-bandgap fused-ring electron acceptor (IDIC)-based organic solar cells, which exhibit power conversion efficiencies of up to 11%.

Structures and receptor binding of hemagglutinins from human-infecting H7N9 influenza viruses.

Two Viruses to Bind Structural studies of two different H7N9 influenza viruses isolated from humans—A/Shanghai/1/2013 and A/Anhui/1/2013—which have different amino acid sequences in the receptor binding site, provide data indicating that the virus is in transition with respect to host adaptation. The Shanghai virus was one of the first isolated in humans that binds avian receptor glycans with high affinity, but binds poorly to human receptors. However, the later Anhui isolates can bind both avian and human receptors at high affinity. Shi et al. (p. 243, published online 5 September) show that four hydrophobic mutations contribute to acquisition of affinity for the human receptor by the virus hemagglutinin (HA) and confirm this effect in binding studies with virus particles. Further comparison of a mutant H7N9 A/Anhui/1/2013 HA with the bird flu H5N1 virus revealed the significance of some of the naturally occurring changes observed in circulating H7N9 viruses, which helps to explain how these viruses have been able to cause many severe human infections in a short time. Four amino acids in the H7N9 influenza virus binding site provide a hydrophobic environment for human receptors. An avian-origin human-infecting influenza (H7N9) virus was recently identified in China. We have evaluated the viral hemagglutinin (HA) receptor–binding properties of two human H7N9 isolates, A/Shanghai/1/2013 (SH-H7N9) (containing the avian-signature residue Gln226) and A/Anhui/1/2013 (AH-H7N9) (containing the mammalian-signature residue Leu226). We found that SH-H7N9 HA preferentially binds the avian receptor analog, whereas AH-H7N9 HA binds both avian and human receptor analogs. Furthermore, an AH-H7N9 mutant HA (Leu226 → Gln) was found to exhibit dual receptor-binding property, indicating that other amino acid substitutions contribute to the receptor-binding switch. The structures of SH-H7N9 HA, AH-H7N9 HA, and its mutant in complex with either avian or human receptor analogs show how AH-H7N9 can bind human receptors while still retaining the avian receptor–binding property.

Conjugated Zwitterionic Polyelectrolyte as the Charge Injection Layer for High-Performance Polymer Light-Emitting Diodes

A new zwitterionic conjugated polyelectrolyte without free counterions has been used as an electron injection material in polymer light-emitting diodes. Both the efficiency and maximum brightness were considerably improved in comparison with standard Ca cathode devices. The devices showed very fast response times, indicating that the improved performance is, in addition to hole blocking, due to dipoles at the cathode interface, which facilitate electron injection.

Raman scattering study of zinc blende and wurtzite ZnS

We have conducted an experimental and theoretical study on first- and second-order Raman scattering of zinc blende and wurtzite ZnS. Based on the calculated phonon band structure, phonon density of states, and symmetry selection rules, we have clearly identified for the first time the origins of these vibration modes in the second-order Raman spectra from these two polymorphs. For zinc blende ZnS, it is found that the previously estimated frequency of the LA mode at X point in the Brillouin-zone boundary is much smaller than the value obtained from other experiments and our calculation. Considering the involvement of LA phonon at X point, we reassign the second-order Raman active modes and some other modes which have not yet been understood so far. This work clarifies some of the controversial Raman mode assignments in zinc blende and wurtzite ZnS.

Facile synthesis of nickel oxide nanotubes and their antibacterial, electrochemical and magnetic properties

Nickel oxide nanotubes with great antibacterial activities, electrochemical capacitance, and magnetic properties have been synthesized through a precursor method with dimethylglyoxime as precipitant for the precursor, and the method has been developed for the synthesis of Ni/C nanorods.