A novel functionalized graphdiyne oxide membrane for efficient removal and rapid detection of mercury in water.

In practice, efficient, rapid and simple removal of Hg(II) from water using nano adsorbents remains an extreme challenge at present. In this work, a novel Hg(II) adsorbent based on functionalized graphdiyne oxide (GDYO-3M) membrane was designed for the purpose of effective and prompt removal of Hg(II) from environmental water for the first time. Through filtration, the proposed GDYO-3M membrane (4 cm diameter size) fulfilled an exceeding 97% removal efficiency in > 10 L water containing 0.1 mg/L Hg(II) within 1 h. Due to the presence of -SH groups, the GDYO-3M membrane demonstrates an excellent selectivity for Hg(II) vs. 14 co-existing metal ions. In the meantime, the GDYO-3M membrane represents a favorable reproducibility (above 95% Hg(II) removal) after 9 successive adsorption-desorption cycles. For the mechanism, it is believed that the active sites in the adsorption process mainly include -SH groups, oxygen-containing functional groups, and alkyne bonds. Further, the GDYO-3M membrane can be utilized as an enrichment approach for sensitive analysis of Hg(II) in water based on energy dispersion X-ray fluorescence spectrometry (ED-XRF), whose detection limit (LOD) reaches 0.2 µg/L within 15 min. This work not only provides a green and efficient method for removing Hg(II), but also renders an approach for rapid, sensitive and portable Hg(II) detection in water.

Lewis-Acid-Promoted Ligand-Controlled Regiodivergent Cycloaddition of Pd-Oxyallyl with 1,3-Dienes: Reaction Development and Origins of Selectivities.

For nearly 30 years, considerable research effort has been focused on the development of methods for catalytic (3 + 2) cycloaddition reactions of palladium-oxyallyl species with alkenes. However, because C-O bond formation is kinetically favored, the (3 + 2) cycloadditions achieved to date have involved C-O reductive elimination. We herein report a method of lithium triflate-promoted (3 + 2) cycloaddition reactions of palladium-oxyallyl species with 1,3-dienes that proceed via a pathway terminated with C-C bond formation to give a five-membered carbocycle. Coordination of the lithium ion with the alkoxide moiety disrupts the C-O reductive elimination and forms a metal-enolate tethered π-allyl-Pd. The π-allyl-Pd moiety then accepts intramolecular allylic attack from the enolate moiety to form carbocyclic products. Furthermore, by tuning the steric properties of the palladium ligand, we could also accomplish the competing (4 + 3) cycloadditions, and thus this method provides regiodivergent access to both cyclopentanones and cycloheptanones. The reaction mechanism was investigated by DFT calculation and the origins of the regioselectivities of the cycloaddition were rationalized.

Stereodivergent Coupling of 1,3-Dienes with Aldimine Esters Enabled by Synergistic Pd and Cu Catalysis.

Herein we describe the use of synergistic Pd and Cu catalysis for stereodivergent coupling reactions between 1,3-dienes and aldimine esters. By using different enantiomers of the two metal catalysts, all four stereoisomers of the coupling products, which have two vicinal stereocenters, could be accessed with high diastereo- and enantioselectivity. This atom-economical cross-coupling reaction has a wide substrate scope and good functional group tolerance. Our work highlights the power of synergistic catalysis for asymmetric coupling reactions involving Pd-hydride catalysts.

Comparative transcriptome analysis reveals unique genetic adaptations conferring salt tolerance in a xerohalophyte.

Most studies on salt tolerance in plants have been conducted using glycophytes like Arabidopsis thaliana (L.) Heynh., with limited resistance to salinity. The xerohalophyte Zygophyllum xanthoxylum (Bunge) Engl. is a salt-accumulating desert plant that efficiently transports Na+ into vacuoles to manage salt and exhibits increased growth under salinity conditions, suggesting a unique transcriptional response compared with glycophytes. We used transcriptome profiling by RNA-seq to compare gene expression in roots of Z. xanthoxylum and A. thaliana under 50 mM NaCl treatments. Gene Ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis suggested that 50 mM NaCl was perceived as a stimulus for Z. xanthoxylum whereas a stress for A. thaliana. Exposure to 50 mM NaCl caused metabolic shifts towards gluconeogenesis to stimulate growth of Z. xanthoxylum, but triggered defensive systems in A. thaliana. Compared with A. thaliana, a vast array of ion transporter genes was induced in Z. xanthoxylum, revealing an active strategy to uptake Na+ and nutrients from the environment. An ascorbate-glutathione scavenging system for reactive oxygen species was also crucial in Z. xanthoxylum, based on high expression of key enzyme genes. Finally, key regulatory genes for the biosynthesis pathways of abscisic acid and gibberellin showed distinct expression patterns between the two species and auxin response genes were more active in Z. xanthoxylum compared with A. thaliana. Our results provide an important framework for understanding unique patterns of gene expression conferring salt resistance in Z. xanthoxylum.

The synergistic effects of sodium and potassium on the xerophyte Apocynum venetum in response to drought stress.

Apocynum venetum is an eco-economic plant species with high adaptability to saline and arid environments. Our previous work has found that A. venetum could absorb large amount of Na+ and maintain high K+ level under saline conditions. To investigate whether K+ and Na+ could simultaneously enhance drought resistance in A. venetum, seedlings were exposed to osmotic stress (-0.2 MPa) in the presence or absence of additional 25 mM NaCl under low (0.01 mM) and normal (2.5 mM) K+ supplying conditions, respectively. The results showed that A. venetum should be considered as a typical K+-efficient species since its growth was unimpaired and possessed a strong K+ uptake and prominent K+ utilization efficiency under K+ deficiency condition. Leaf K+ concentration remained stable or was even significantly increased under osmotic stress in the presence or absence of NaCl, compared with that under control condition, regardless of whether the K+ supply was sufficient or not, and the contribution of K+ to leaf osmotic potential consistently exceeded 37%, indicating K+ is the uppermost contributor to osmotic adjustment of A. venetum. Under osmotic stress, the addition of 25 mM NaCl significantly increase Na+ accumulation in leaves and the contribution of Na+ to osmotic adjustment, thus improving the relative water content, concomitantly, promoting the photosynthetic activity resulting in an enhancement of overall plant growth. These findings suggested that, K+ and Na+ simultaneously play crucial roles in the osmotic adjustment and the maintenance of water status and photosynthetic activity, which is beneficial for A. venetum to cope with drought stress.

Gold Nanoparticle-Based Probe for Colorimetric Detection of Copper Ions.

A new ligand 10-mercaptodecyl-1-iminodiacetic acid (MDIA) was synthesized and used to modify gold nanoparticles to provide a simple assay to repeatedly sense Cu²âº in the solution at room temperature. This functionalized gold nanosensor was applied for the detection of Cu²âº in water samples with sensitivity and simplicity. The chelation/aggregation process is reversible via addition of a strong metal ion chelator such as EDTA. This simple and fast colorimetric sensor is important in the application of copper ion detection in water quality during the emergency and early warning monitoring.