A facile approach for morphosynthesis of Pd nanoelectrocatalysts

A facile approach has been developed for synthesis of highly-structured, anisotropic Pd nanostructures. The dendritic Pd nanostructures show superior performance toward oxidation of formic acid and methanol for fuel cell application.     

Low dissipative entropy stable schemes using third order WENO and TVD reconstructions

A low dissipative framework is given to construct high order entropy stable flux by addition of suitable numerical diffusion operator into entropy conservative flux. The framework is robust in the sense that it allows the use of high order reconstructions which satisfy the sign property only across the discontinuities. The third order weighted essentially non-oscillatory (WENO) interpolations and high order total variation diminishing (TVD) reconstructions are shown to satisfy the sign property across discontinuities. Third order accurate entropy stable schemes are constructed by using third order WENO and high order TVD reconstructions procedures in the diffusion operator. These schemes are efficient and less diffusive since the diffusion is actuated only in the sign stability region of the used reconstruction which includes discontinuities. Numerical results with constructed schemes for various test problems are given which show the third order accuracy and less dissipative nature of the schemes.     

Chemical Degradation of Mercury Alkyls Mediated by Copper Selenide Nanosheets

Methylation and demethylation of mercury compounds are two important competing processes that control the net production of highly toxic mercury alkyls, methylmercury (MeHg⁺) and dimethylmercury (Me₂Hg), in environment. Although the microbial and the photochemical methylation and demethylation processes are well studied in recent years but the chemical methylation and demethylation processes have not been studied well. Herein, we report for the first time that the CuSe nanosheet has remarkable ability to activate the highly inert Hg?C bonds of various MeHg⁺ and Me₂Hg compounds at room temperature (21 °C). It facilitates the conversion of MeHg⁺ into Me₂Hg in the absence of any proton donors. Whereas, in the presence of any proton source, it has unique ability to degrade MeHg⁺ into CH₄ and inorganic mercury (Hg²⁺). Detailed studies revealed that the relatively fast Hg?C bond cleavage was observed in case of MeHgSPh or MeHgI in comparison to MeHgCl, indicating that the Hg?C bond in MeHgCl is relatively inert in nature. On the other hand, the Hg?C bond in Me₂Hg is considered to be exceedingly inert and, thus, difficult to cleave at room temperature. However, CuSe nanosheets showed unique ability to degrade Me₂Hg into CH₄ and Hg²⁺, via the formation of MeHg⁺, under acidic conditions at room temperature. DFT calculations revealed that the Hg?C bond activation occurs through adsorption on the surface of (100)‐faceted CuSe nanosheets.     

Stable Copper(I)‐Mediated Base Pairing in DNA

A GNA (glycol nucleic acid) functionalized nucleoside analogue containing the artificial nucleobase 1H‐imidazo[4,5‐f][1,10]phenanthroline (P) was used to form a copper(I)‐mediated base pair within a DNA duplex. The geometrical constraints imposed by the artificial nucleobase play a pivotal role in this unprecedented stabilization of copper(I) in aqueous medium via metal‐mediated base pairing. The formation of the copper(I)‐mediated base pair was investigated by temperature‐dependent UV spectroscopy and CD spectroscopy. The metal‐mediated base pair stabilizes the DNA oligonucleotide duplex by 23 °C. A redox chemistry approach confirmed that this base pair formation was due to the incorporation of copper(I) into the duplex. This first report of a copper(I)‐mediated base pair adds metal‐based diversity to the field and consequently opens up the range of possible applications of metal‐modified nucleic acids.