Covalent Organic Framework with Highly Accessible Carbonyls and π-Cation Effect for Advanced Potassium-Ion Batteries.

Covalent organic frameworks (COF) possess a robust and porous crystalline structure, making them an appealing candidate for energy storage. Herein, we report an exfoliated polyimide COF composite (P-COF@SWCNT) prepared by an in situ condensation of anhydride and amine on the single-walled carbon nanotubes as advanced anode for potassium-ion batteries (PIBs). Numerous active sites exposed on the exfoliated frameworks and the various open pathways promote the highly efficient ion diffusion in the P-COF@SWCNT while preventing irreversible dissolution in the electrolyte. During the charging/discharging process, K+ is engaged in the carbonyls of imide group and naphthalene rings through the enolization and π-K+ effect, which is demonstrated by the DFT calculation and XPS, ex-situ FTIR, Raman. As a result, the prepared P-COF@SWCNT anode enables an incredibly high reversible specific capacity of 438 mA h g-1 at 0.05 A g-1 and extended stability. The structural advantage of P-COF@SWCNT enables more insights into the design and versatility of COF as an electrode.

Two Co(II)/Ni(II) complexes based on nitrogenous heterocyclic ligands as high-performance electrocatalysts for the hydrogen evolution reaction.

Two transition metal complexes {[Co2(bpda)4(H2O)2]·4H2O}n(Co-1) and {[Ni(bpda)2(H2O)2]·2H2O}(Ni-2) (H2bpda = 2,2'-bipyridine-4,4'-dicarboxylic acid) have been synthesized by a hydrothermal method and characterized. These two compounds can be explored as stable electrocatalysts in the hydrogen evolution reaction (HER) using two important parameters: the overpotential and Tafel slope (TS). Electrochemical studies suggest that the reaction kinetics of a Co-1 catalyst is more favorable than that of a Ni-2 catalyst. Co-1 exhibits better HER performance with an overpotential of 182 mV at a current density of 10 mA cm-2, a small TS of 87.21 mV dec-1 and superior long-term durability (of up to 3000 cycles). Structural analysis shows that its catalytic activity is improved due to the two mixed valence cobalt ions and the pore structure formed by hydrogen bonds in Co-1, which is different from that of Ni-2. In addition, the mechanism of the HER is also explained theoretically by DFT molecular orbital and free energy calculations in this article.

Regulating the Li Nucleation/Growth Behavior via Cu2O Nanowire Array and Artificial Solid Electrolyte Interphase toward Highly Stable Li Metal Anode.

Lithium (Li) metal has been considered to be the most promising anode material for next-generation rechargeable batteries. Unfortunately, the hazards induced by dendrite growth and volume fluctuation hinder its commercialized application. Here, a three-dimensional (3D) current collector composed of a vertically aligned Cu2O nanowire that is tightly coated with a polydopamine protective layer is developed to solve the encountered issues of lithium metal batteries (LMBs). The Cu2O nanowire arrays (Cu2O NWAs) provide abundant lithiophilic sites for inducing Li nucleation selectively to form a thin Li layer around the nanowires and direct subsequent Li deposition. The well-defined nanochannel works well in confining the Li growth spatially and buffering the volume change during the repeated cycling. The PDA coatings adhered onto the outline of the Cu2O NWAs serve as the artificial solid electrolyte interface to isolate the electrode and electrolyte and retain the interfacial stability. Moreover, the increased specific area of copper foam (CF) can dissipate the local current density and further suppress the growth of Li dendrites. As a result, CF@Cu2O NWAs@PDA realizes a dendrite-free morphology and the assembled symmetrical batteries can work stably for over 1000 h at 3 mA cm-2. When CF@Cu2O NWAs@PDA is coupled with a LiFePO4 cathode, the full cells exhibit improved cycle stability and rate performance.

Stubby or Slender? Ear Architecture Is Related to Drought Resistance in Maize.

Ear architecture is determined by two stable heritable traits, kernel row number (KRN) and kernel number per row (KNPR), but its relationship with drought resistance is still vague. To this end, we obtained 16 and 11 hybrids with slender (less KRN but more KNPR) and stubby (more KRN but less KNPR) ears by intentionally crossbreeding, respectively. These hybrids were exposed to a seven-day water deficit (WD) since silk emergence coupled with synchronous (SP) and continuous pollination (CP) to alter the pollination time gaps on ears. The results showed that the emerged silks in CP were 9.1 and 9.0% less than in the SP treatment in the stubby and slender ears, respectively, suggesting the suppression of asynchronous pollination on silk emergence. The stubby ears performed higher silking rate and yield compared with the slender ears with or without drought stress. To eliminate the inherent difference in sink capacities, we selected four hybrids for each ear type with similar silk and kernel numbers for further analyses. Interestingly, the stubby ears were less affected in silking rate and thus performed higher yield under drought compared with the slender ears. The finding suggests that ear architecture matters in the determination of drought resistance that deserves more attention in breeding.

Lanthanide complexes based on a conjugated pyridine carboxylate ligand: structures, luminescence and magnetic properties.

Three lanthanide compounds have been synthesized, namely, {[Dy2(bpda)3(H2O)3]4·2H2O}(Dy-1), {[Sm(bpda)2·(H2O)]·H2O} n (Sm-2) and {[Tb2(bpda)3(H2O)3]4·2H2O} (Tb-3) (H2bpda = 2,2'-bipyridine-6,6'-dicarboxylic acid). Their structures were determined by single crystal X-ray diffraction and characterized by elemental analysis, infrared spectroscopy and thermogravimetric analysis. Dy-1 and Tb-3 are isostructural with a conjugate bimolecular four-nuclear cluster structure constructed with intramolecular hydrogen bonds and they form a 3D supramolecular structure with intermolecular hydrogen bonding. Sm-2 is a one-dimensional chain structure and is further connected by intricate hydrogen bonds into a three-dimensional supramolecular structure. These three compounds exhibit significant characteristic luminescence from the ligand to the central Ln(iii) ion, which is found by solid-state photoluminescence measurement. Sm-2 exhibits a long luminescence lifetime and high fluorescence quantum yield. A slow relaxation phenomenon is observed for the dysprosium compound by measuring the alternating-current susceptibility at low temperature and the underlying mechanism was further confirmed by theoretical calculations.

Correction: Lanthanide complexes based on a conjugated pyridine carboxylate ligand: structures, luminescence and magnetic properties.

[This corrects the article DOI: 10.1039/C9RA10975G.].

[Generation of chemical-inducible activation tagging T-DNA insertion lines of Arabidopsis thaliana].

Using an estrogen-inducible expression XVE (LexA-VP16-Estragon Receptor) system, we have generated approximately 40 000 independent T-DNA insertion lines of Arabidopsis thaliana. Segregation analyses of about 18000 lines indicated that 51.6% of them contain single T-DNA insertions and that the average insertion number is 1.38 copies per line. Mutants displaying a variety of morphological alterations were identified, including those that affect development of roots,hypocotyls, leaves, floral organs and seeds as well as the flowering time.

Controlling silk fibroin microspheres via molecular weight distribution.

Silk fibroin (SF) microspheres were produced by salting out SF solution via the addition of potassium phosphate buffer solution (K2HPO4-KH2PO4). The morphology, size and polydispersity of SF microspheres were adjusted by changing the molecular weight (MW) distribution and concentration of SF, as well as the ionic strength and pH of the buffer solution. Changing the conditions under which the SF fiber dissolved in the Lithium Boride (LiBr) solution resulted in altering the MW distribution of SF solution. Under optimal salting-out conditions (ionic strength>0.7 M and pH>7) and using a smaller and narrower SF MW distribution, SF microspheres with smoother shapes and more uniform sizes were produced. Meanwhile, the size and polydispersity of the microspheres increased when the SF concentration was increased from 0.25 mg/mL to 20 mg/mL. The improved SF microspheres, obtained by altering the distribution of molecular weight, have potential in drug and gene delivery applications.

Arabidopsis RAV1 is down-regulated by brassinosteroid and may act as a negative regulator during plant development.

RAV1 is a novel DNA-binding protein with two distinct DNA-binding domains unique in higher plants, but its role in plant growth and development remains unknown. Using cDNA array, we found that transcription of RAV1 is down-regulated by epibrassinolide (epiBL) in Arabidopsis suspension cells. RNA gel blot analysis revealed that epiBL-regulated RAV1 transcription involves neither protein phosphorylation/dephosphorylation nor newly synthesized protein, and does not require the functional BRI1, suggesting that this regulation might be through a new BR signaling pathway. Overexpressing RAV1 in Arabidopsis results in a retardation of lateral root and rosette leaf development, and the underexpression causes an earlier flowering phenotype, implying that RAV1 may function as a negative regulatory component of growth and development.

[Characterization of an ultra-violet inducible gene that encodes glutathione S-transferase in Arabidopsis thaliana].

Glutathione S-transterased (GSTs) are a highly divergent gene family. They play important roles not only in many stress responses, but also in plant growth and development. To understand whether the GST can protect plant from the damage of ultra-violet (UV) radiation, a UV inducible GST gene was isolated from an Arabidopsis cDNA library. The plant expression vector containing the GST cDNA was constructed and transferred into Arabidopsis thaliana plants by the Agrobacterium-mediated vacuum method. Molecular genetic analyses showed that the overexpression of the UV inducible GST could increase the tolerance of the transgenic plants to UV radiation.

Genome-wide ORFeome cloning and analysis of Arabidopsis transcription factor genes.

Here, we report our effort in generating an ORFeome collection for the Arabidopsis transcription factor (TF) genes. In total, ORFeome clones representing 1,282 Arabidopsis TF genes have been obtained in the Gateway high throughput cloning pENTR vector, including 411 genes whose annotation lack cDNA support. All the ORFeome inserts have also been mobilized into a yeast expression destination vector, with an estimated 85% rate of expressing the respective proteins. Sequence analysis of these clones revealed that 34 of them did not match with either the reported cDNAs or current predicted open-reading-frame sequences. Among those, novel alternative splicing of TF gene transcripts is responsible for the observed differences in at least five genes. However, those alternative splicing events do not appear to be differentially regulated among distinct Arabidopsis tissues examined. Lastly, expression of those TF genes in 17 distinct Arabidopsis organ types and the cultured cells was profiled using a 70-mer oligo microarray.