In view of the limited ruthenium resource, metal-free organic dyes may play a prominent role in the coming large-scale application of cost-effective dye-sensitized solar cells, if their efficiency and stability can be considerably improved. In this paper we utilized a binary π-conjugated spacer of ethylenedioxythiophene and dithienosilole to construct a high molar absorption coefficient push-pull dye, characteristic of an intramolecular charge-transfer band peaking at 584 nm measured in chloroform. In comparison with the standard ruthenium sensitizer Z907, this metal-free chromophore C219 endowed a nanocrystalline titania film with an evident light-harvesting enhancement, leading to an unprecedented 10.0-10.3% efficiency at the AM1.5G conditions for dyesensitized solar cells with nonruthenium dyestuffs, although a highly volatile electrolyte was used. Transient absorption measurements have revealed that even if the kinetics of back-electron transfer and dye regeneration are considerably different for Z907 and C219, the branching ratios of these two charge-transfer channels are over 35 for both dyes, ensuring a high yield of net charge separation at the titania/dye/electrolyte interface. A solvent-free ionic liquid cell with C219 as the sensitizer exhibited an impressive efficiency of 8.9% under a low light intensity of 14.39 mW cm -2 , making it very favorable for the indoor application of flexible dye-sensitized solar cells.

The recent outbreaks of SARS-CoV-2 pose a global health emergency. The SARS-CoV-2 trimeric spike (S) glycoprotein interacts with the human ACE2 receptor to mediate viral entry into host cells. We report the cryo-EM structures of a tightly closed SARS-CoV-2 S trimer with packed fusion peptide and an ACE2-bound S trimer at 2.7- and 3.8-Å resolution, respectively. Accompanying ACE2 binding to the up receptor-binding domain (RBD), the associated ACE2-RBD exhibits continuous swing motions. Notably, the SARS-CoV-2 S trimer appears much more sensitive to the ACE2 receptor than the SARS-CoV S trimer regarding receptor-triggered transformation from the closed prefusion state to the fusion-prone open state, potentially contributing to the superior infectivity of SARS-CoV-2. We defined the RBD T470-T478 loop and Y505 as viral determinants for specific recognition of SARS-CoV-2 RBD by ACE2. Our findings depict the mechanism of ACE2-induced S trimer conformational transitions from the ground prefusion state toward the postfusion state, facilitating development of anti–SARS-CoV-2 vaccines and therapeutics.

Owing to the growing heat removal issue of modern electronic devices, polymer composites with high thermal conductivity have drawn much attention in the past few years. However, a traditional method to enhance the thermal conductivity of the polymers by addition of inorganic fillers usually creates composite with not only limited thermal conductivity but also other detrimental effects due to large amount of fillers required. Here, novel polymer composites are reported by first constructing 3D boron nitride nanosheets (3D-BNNS) network using ice-templated approach and then infiltrating them with epoxy matrix. The obtained polymer composites exhibit a high thermal conductivity (2.85 W m(-1) K(-1)), a low thermal expansion coefficient (24-32 ppm K(-1)), and an increased glass transition temperature (T(g)) at relatively low BNNSs loading (9.29 vol%). These results demonstrate that this approach opens a new avenue for design and preparation of polymer composites with high thermal conductivity. The polymer composites are potentially useful in advanced electronic packaging techniques, namely, thermal interface materials, underfill materials, molding compounds, and organic substrates.