GFS9/TT9 contributes to intracellular membrane trafficking and flavonoid accumulation in Arabidopsis thaliana

Flavonoids are the most important pigments for the coloration of flowers and seeds. In plant cells, flavonoids are synthesized by a multi‐enzyme complex located on the cytosolic surface of the endoplasmic reticulum, and they accumulate in vacuoles. Two non‐exclusive pathways have been proposed to mediate flavonoid transport to vacuoles: the membrane transporter‐mediated pathway and the vesicle trafficking‐mediated pathway. No molecules involved in the vesicle trafficking‐mediated pathway have been identified, however. Here, we show that a membrane trafficking factor, GFS9, has a role in flavonoid accumulation in the vacuole. We screened a library of Arabidopsis thaliana mutants with defects in vesicle trafficking, and isolated the gfs9 mutant with abnormal pale tan‐colored seeds caused by low flavonoid accumulation levels. gfs9 is allelic to the unidentified transparent testa mutant tt9. The responsible gene for these phenotypes encodes a previously uncharacterized protein containing a region that is conserved among eukaryotes. GFS9 is a peripheral membrane protein localized at the Golgi apparatus. GFS9 deficiency causes several membrane trafficking defects, including the mis‐sorting of vacuolar proteins, vacuole fragmentation, the aggregation of enlarged vesicles, and the proliferation of autophagosome‐like structures. These results suggest that GFS9 is required for vacuolar development through membrane fusion at vacuoles. Our findings introduce a concept that plants use GFS9‐mediated membrane trafficking machinery for delivery of not only proteins but also phytochemicals, such as flavonoids, to vacuoles.     

Coated Lithium Powder (CLiP) Electrodes for Lithium‐Metal Batteries

Safety issues caused by the metallic lithium inside a battery represent one of the main reasons for the lack of commercial availability of rechargeable lithium‐metal batteries. The advantage of anodes based on coated lithium powder (CLiP), compared to plain lithium foil, include the suppression of dendrite formation, as the local current density during stripping/plating is reduced due to the higher surface area. Another performance and safety advantage of lithium powder is the precisely controlled mass loading of the lithium anode during electrode preparation, giving the opportunity to avoid Li excess in the cell. As an additional benefit, the coating makes electrode manufacturing safer and eases handling. Here, electrodes based on coated lithium powder electrodes (CLiP) are introduced for application in lithium‐metal batteries. These electrodes are compared to lithium foil electrodes with respect to cycling stability, coulombic efficiency of lithium stripping/plating, overpotential, and morphology changes during cycling.     

Very High Surface Capacity Observed Using Si Negative Electrodes Embedded in Copper Foam as 3D Current Collectors

Cu foam is evaluated as a replacement for metal foil current collectors to create 3D composite electrodes with the objective to produce Si‐based anodes with high loadings. The electrodes are prepared by casting the slurry into the porosity of the foam. With such a design, the loading and the surface capacity can reach values as high as 10 mg cm^?2 and 10 mAh cm^?2. Compared to the common 2D design, the 3D copper framework shows a great advantage in the cycle life (more than 400 cycles at a Si loading of 10 mg cm^?2 with commercial micrometric particles) and power performance. The thinness of the composite coating on the foam walls favors a better preservation of the electronic wiring upon cycling and fast lithium ion diffusion. A higher coulombic efficiency in half cells with lithium metal as the counter electrode is achieved by using carbon nanofibers (CNF) rather than carbon black (CB). The possibility to reach, in practice, higher surface capacity could allow a significant increase in both the volumetric and gravimetric energy densities by 23% and 19%, respectively, for the Cu foam‐silicon//LiFePO₄ stack compared to the graphite/LiFePO₄ stack of traditional design.     

High‐Performance,Transparent, Dye‐Sensitized Solar Cells for See‐Through Photovoltaic Windows

Dye‐sensitized solar cells (DSCs) have attracted great interest as one of the most promising photovoltaic technologies, and transparent DSCs show potential applications as photovoltaic windows. However, the competition between light absorption for photocurrent generation and light transmittance for obtaining high transparency limits the performance of transparent DSCs. Here, transparent DSCs exhibiting a high light transmittance of 60.3% and high energy conversion efficiency (3.66%) are reported. The strategy is to create a cocktail system composed of ultraviolet and near‐infrared dye sensitizers that selectively and efficiently harvest light in the invisible or low‐eye‐sensitivity region while transmitting light in high‐eye‐sensitivity regions. This new design provides a reasonable approach for realizing high efficiency and transparency DSCs that have potential applications as photovoltaic windows.     

Identifying the Impact of Surface Recombination at Electrodes in Organic Solar Cells by Means of Electroluminescence and Modeling

This work reports on combining current‐voltage characteristics, electroluminescence (EL) measurements, and modeling to identify the selectivity of the electrodes in bulk‐heterojunction organic solar cells. Devices with the same photoactive layer but different contact materials are compared and the impact of surface recombination at the contacts on their performance is determined. The open‐circuit voltage, V _OC, depends strongly on the selectivity of the electrodes and it is observed that the EL signal of cells with lower V _OC is dramatically reduced. This is ascribed to an enhanced rate of surface recombination, which is a non‐radiative recombination pathway and does therefore not contribute to the EL yield. In addition, these cells have a lower current in forward direction despite the fact that the surface recombination occurs in addition to the recombination in the bulk. A theoretical model was set up and in the corresponding numerical simulations all three findings (lower V _OC, strongly reduced EL signal and lower forward current) could be clearly reproduced by varying just one single parameter which determines the selectivity of the electrode.     

Quantum‐Dot Sensitized Solar Cells Employing Hierarchical Cu2S Microspheres Wrapped by Reduced Graphene Oxide Nanosheets as Effective Counter Electrodes

Hierarchical Cu₂S microspheres wrapped by reduced graphene oxide (RGO) nanosheets are prepared via a one‐step solvothermal process. The amount of graphene oxide used in the synthesis process has a remarkable effect on the features of Cu₂S microspheres. Compared to Pt and Cu₂S electrodes, RGO‐Cu₂S electrodes show better electrocatalytic activity, greater stability, lower charge‐transfer resistance, and higher exchange current density. As expected, RGO‐Cu₂S electrodes exhibit superior performance when functioning as counter electrodes in CdS/CdSe quantum dot‐sensitized solar cells (QDSSCs) using a polysulfide electrolyte. A power conversion efficiency up to 3.85% is achieved for the QDSSC employing an optimized RGO‐Cu₂S counter electrode, which is higher than those of the QDSSCs featuring Pt (2.14%) and Cu₂S (3.39%) counter electrodes.