Shiwei Cao

An embryo of protocells: The capsule of graphene with selective ion channels

The synthesis of artificial cell is a route for searching the origin of protocell. Here, we create a novel cell model of graphene capsules with selective ion channels, indicating that graphene might be an embryo of protocell membrane. Firstly, we found that the highly oxidized graphene and phospholipid-graphene oxide composite would curl into capsules under a strongly acidic saturated solution of heavy metallic salt solution at low temperature. Secondly, L-amino acids exhibited higher reactivity than D-amino acids on graphene oxides to form peptides, and the formed peptides in the influence of graphene would be transformed into a secondary structure, promoting the formation of left-handed proteins. Lastly, monolayer nanoporous graphene, prepared by unfocused 84Kr25+, has a high selectivity for permeation of the monovalent metal ions ( Rb+ > K+ > Cs+ > Na+ > Li+, based on permeation concentration), but does not allow Cl- go through. It is similar to K+ channels, which would cause an influx of K+ into capsule of graphene with the increase of pH in the primitive ocean, creating a suitable inner condition for the origin of life. Therefore, we built a model cell of graphene, which would provide a route for reproducing the origin of life.

Solvent extraction of americium(III) and europium(III) with tridentate N,N-dialkyl-1,10-phenanthroline-2-amide-derived ligands: extraction, complexation and theoretical study

The extraction and complexation behavior of soft–hard combined N,N-dialkyl-1,10-phenanthroline-2-amide (PTA) ligands with Am(III) and Eu(III) in HNO3 solution was investigated. The effects of acidity of the aqueous solution, shaking time, concentration of the extractant and temperature on the distribution ratios were studied. The extraction ability for both Am(III) and Eu(III) was found to decrease with an increase in the length of the substituent alkyl chains, and the highest extractability and selectivity for Am(III) over Eu(III) were found for the diethyl-substituted ligand. The separation factor for Am(III) over Eu(III) reached around 7.6 at low acidity and high salinity. UV-vis titrations revealed that the dialkyl-substituted tridentate PTAs all predominantly formed 1 : 1 complexes with Eu(III), which agreed well with the results of slope analyses in the extraction experiments. The stability constants (KEuL) as well as the protonation constants (KH) were also determined by UV-vis titration. Computational chemistry gave a good explanation of the relationship between the alkalinity and the protonation energy of the proposed PTA ligands. Density functional theory (DFT) calculations on the optimized structures of Am(III) and Eu(III) complexes with C2-PTA showed that the selectivity may originate from differences in the degree of covalency of the bonds between the metal ions and the donor N atoms, which fits well with the experimental results.

Asymmetrical semisphere nanopores on monolayer graphene for gas permeation

Nanoporous graphene membrane (NGM) has enormous potential and excellent properties in practical applications. But almost all of the previous studies were based on the assumption that the nanopores were symmetric along the normal vector of the graphene plane. Asymmetric nanoporous graphene membrane (A-NGM), a promising membrane material in energy, environment and bionic, was seldom researched until now. A kind of graphene membrane with asymmetric semisphere nanopore embedded in it is designed. Such a membrane is provided with the properties of A-NGM. Its electron properties and van der Waals surface are analyzed by quantum chemistry approach. Permeation mechanism of helium, neon and argon across this graphene membrane is analyzed by employing Langmuir adsorption isotherm. Molecular dynamics simulations are used to characterize the asymmetric performance of A-NGM for gas permeance. The driving force of these dynamical processes is revealed by implementing noncovalent interaction analysis. These results are considered not only assist in the designing of asymmetric membrane material, but also pave the way toward the realization of unidirectional graphene membrane in the future.