Low‐dimensional Ruddlesden–Popper (LDRP) perovskites are a current theme in solar energy research as researchers attempt to fabricate stable photovoltaic devices from them. However, poor exciton ...dissociation and insufficiently fast charge transfer slows the charge extraction in these devices, resulting in inferior performance. 1,4‐Butanediamine (BEA)‐based low‐dimensional perovskites are designed to improve the carrier extraction efficiency in such devices. Structural characterization using single‐crystal X‐ray diffraction reveals that these layered perovskites are formed by the alternating ordering of diammonium (BEA2+) and monoammonium (MA+) cations in the interlayer space (B‐ACI) with the formula (BEA)0.5MAn
PbnI3n+1. Compared to the typical LDRP counterparts, these B‐ACI perovskites deliver a wider light absorption window and lower exciton binding energies with a more stable layered perovskite structure. Additionally, ultrafast transient absorption indicates that B‐ACI perovskites exhibit a narrow distribution of quantum well widths, leading to a barrier‐free and balanced carrier transport pathway with enhanced carrier diffusion (electron and hole) length over 350 nm. A perovskite solar cell incorporating BEA ligands achieves record efficiencies of 14.86% for (BEA)0.5MA3Pb3I10 and 17.39% for (BEA)0.5Cs0.15(FA0.83MA0.17)2.85Pb3(I0.83Br0.17)10 without hysteresis. Furthermore, the triple cations B‐ACI devices can retain over 90% of their initial power conversion efficiency when stored under ambient atmospheric conditions for 2400 h and show no significant degradation under constant illumination for over 500 h.
A new type of ACI perovskite is prepared through the alternating ordering of BEA2+ and MA+ cations in the interlayer space (B‐ACI). The high exciton extraction efficiency and a narrow distribution of quantum well widths of B‐ACI perovskite enable a device with a record efficiency of 17.39%. Furthermore, the devices show stronger resistance to humidity, heating, and light soaks than previous equivalents.
The unique reactivity of indolyl-substituted p -QMs as a new type of two-carbon synthon has been explored for the first time in a novel iron( iii )-catalyzed tandem annulation. This (2+2) ...annulation/retro-4π electrocyclization/imino-Nazarov cyclization cascade reaction is characterized by an unusual structural reconstruction of indolyl-substituted p -QMs, leading to an expeditious assembly of synthetically important functionalized cyclopenta b indoles.
A convenient one‐pot propargylation/amination/cycloisomerization tandem process has been developed for the synthesis of highly substituted pyrroles derivatives from propargylic alcohols, ...1,3‐dicarbonyl compounds and primary amines using indium(III) chloride as a multifunctional catalyst. This method provides a flexible and rapid route to substituted pyrroles.
The leaves of many plants are red during particular stages of their lives, but the adaptive significance of leaf colouration is not yet clearly understood. In order to reveal whether anthocyanins ...play a similar role (i.e. antioxidants) in different seasonal contexts, this study investigated species with red young leaves in the subtropical forest of Dinghushan biosphere reserve (South China) during summer and winter and compared group leaf characteristics between the two seasons. Of 62 total species, 33 exhibited red young leaves in summer only, 6 in winter only, and 23 in both seasons. The anthocyanins extracted from most of these species had an absorption peak at ~530 nm. Frequency distribution analysis showed that the species containing anthocyanins at levels ranging from 0.02 to 0.04 μmol cm
occurred most frequently in summer or winter. Based on conditional grouping of the species, no significant variation was observed in the average anthocyanin contents and antioxidant abilities between summer and winter; the flavonoid content in summer was 2-fold that in winter, whereas the anthocyanin:flavonoid ratio in summer was only half that in winter. Moreover, a positive correlation between anthocyanins and flavonoids was found in summer. Therefore, it is less likely for anthocyanins to serve as antioxidants in summer than winter, because such a function in summer leaves is readily replaced by other flavonoids.
A convenient and efficient Pd(acac)2/Xantphos-catalyzed regioselective hydrosilylation of allenes has been developed. This convenient catalyst proved to be suitable for a broad range of allenes, ...offering a general and efficient route to branched allylsilanes in high yields with exceptional regioselectivity. A Pd(0) species involved mechanism is proposed.
A miniaturized neutron spin flipper based on a high-
T
C
superconductor film, developed at the China Spallation Neutron Source (CSNS), is presented. A neutron spin flipper is an essential component ...for performing polarized neutron experiments and, as such, constitutes a high priority for developing CSNS’s polarized neutron capability. To provide the beamlines with a universal neutron spin flipper operating over a wide wavelength band, the neutron spin flipper utilizes non-adiabatic spin flipping during transit through opposite magnetic fields that are mutually shielded by the superconductor Meissner effect. A compact vacuum heat shield and a low-power consumption sterling refrigerator maintained the superconducting condition while reducing the size and power input of the flipper. The prototype device was tested at the CSNS BL-20, which demonstrated a flipping efficiency of 99% at 4 Å.
The presence of anthocyanins in young leaves plays an important role in mitigation against photodamage and allows leaves to grow and develop normally. Many studies have reported that foliar ...anthocyanins are distributed within the vacuoles of mesophyll cells, so we explored the novel defence style of anthocyanin-coated young leaves of Castanopsis fissa, a dominant subtropical forest tree species, via removable trichomes. Anthocyanins were distributed in C. fissa leaf trichomes, which produced a red coating for the young leaves. As young leaves developed and then matured, the thickness and density of the anthocyanin trichomes progressively decreased, the coating finally disappearing, allowing greater utilization of light by mature leaves. In addition to anthocyanins, the trichomes contained a remarkably high amount of phenolics, which enable the red coating to be more efficient in screening ultraviolet light. Compared with mature leaves, the young leaves exhibited lower photosynthetic ability, which was attributable to the reduced chlorophyll and Rubisco contents. Removal of the red coating had little effect on the photosynthetic capacity of young leaves. However, the young leaves without the coating suffered greater light-induced photoinhibition due to greater excess light entering the chloroplast and the production of H
O
Our results suggest that the anthocyanin coating is photoprotective and this anthocyanin defence style may be a metabolically cost-effective way of adjusting the anthocyanin content in response to demand.
High-entropy alloy layer up to 150 lm in thickness was formed on H13 substrate with a metallurgical bonding at the coating/substrate interface. Simple solid solution phases were formed in the coating ...layer with a typical microstructure composed of both dendrite and interdendrite. The microstructure at the top of the cladding zone consists of equiaxed grains while that at the bottom consists of columnar grains. The coating layer exhibits great enhancement in microhardness and wear resistance compared with the H13 substrate.
A unified strategy toward asymmetric divergent syntheses of nine C8-ethano-bridged diterpenoids A1–A9 (candol A, powerol, sicanadiol, epi-candol A, atisirene, ent-atisan-16α-ol, ...4-decarboxy-4-methyl-GA12, trachinol, and ent-beyerane) has been developed based on late-stage transformations of common synthons having ent-kaurane and ent-trachylobane cores. The expeditious assembly of crucial advanced ent-kaurane- and ent-trachylobane-type building blocks is strategically explored through a regioselective and diastereoselective Fe-mediated hydrogen atom transfer (HAT) 6-exo-trig cyclization of the alkene/enone and 3-exo-trig cyclization of the alkene/ketone, showing the multi-reactivity of densely functionalized polycyclic substrates with πCC and πCO systems in HAT-initiated reactions. Following the rapid construction of five major structural skeletons (ent-kaurane-, ent-atisane-, ent-beyerane-, ent-trachylobane-, and ent-gibberellane-type), nine C8-ethano-bridged diterpenoids A1–A9 could be accessed in the longest linear 8 to 11 steps starting from readily available chiral γ-cyclogeraniol 1 and known chiral γ-substituted cyclohexenone 2, in which enantioselective total syntheses of candol A (A1, 8 steps), powerol (A2, 9 steps), sicanadiol (A3, 10 steps), epi-candol A (A4, 8 steps), ent-atisan-16α-ol (A6, 11 steps), and trachinol (A8, 10 steps) are achieved for the first time.
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