DNA Translocation through Graphene Nanopores

Nanopores -- nanosized holes that can transport ions and molecules -- are very promising devices for genomic screening, in particular DNA sequencing. Both solid-state and biological pores suffer from the drawback, however, that the channel constituting the pore is long, viz. 10-100 times the distance between two bases in a DNA molecule (0.5 nm for single-stranded DNA). Here, we demonstrate that it is possible to realize and use ultrathin nanopores fabricated in graphene monolayers for single-molecule DNA translocation. The pores are obtained by placing a graphene flake over a microsize hole in a silicon nitride membrane and drilling a nanosize hole in the graphene using an electron beam. As individual DNA molecules translocate through the pore, characteristic temporary conductance changes are observed in the ionic current through the nanopore, setting the stage for future genomic screening

Improving Reversible Capacities of High-Surface Lithium Insertion Materials – The Case of Amorphous TiO2

Chemisorbed water and solvent molecules and their reactivity with components from the electrolyte in high-surface nanostructured electrodes remains a contributing factor towards capacity diminishment on cycling in lithium ion batteries due to the limit in maximum annealing temperature. Here we report a marked improvement in the capacity retention of amorphous TiO2 by the choice of preparation solvent, control of annealing temperature and the presence of surface functional groups. Careful heating of the amorphous TiO2 sample prepared in acetone under vacuum lead to complete removal of all molecular solvent and an improved capacity retention of 220 mAh/g over 50 cycles at a C/10 rate. Amorphous TiO2 when prepared in ethanol and heated under vacuum showed an even better capacity retention of 240 mAh/g. From FTIR Spectroscopy and Electron Energy Loss Spectroscopy measurements, the improved capacity is attributed to the complete removal of ethanol and the presence of very small fractions of residual functional groups coordinated to oxygen-deficient surface titanium sites. These displace the more reactive chemisorbed hydroxyl groups, limiting reaction with components from the electrolyte and possibly enhancing the integrity of the solid electrolyte interface (SEI). The present research provides a facile strategy to improve the capacity retention of nanostructured electrode materials

Зміст і закономірності економічного зростання при інтенсифікації виробництва

Composite noble metal-based nanorods for which the surface plasmon resonances can be tuned by composition and geometry are highly interesting for applications in biotechnology, imaging, sensing, optoelectronics, photovoltaics, and catalysis. Here, we present an approach for the oxidative etching and subsequent metal overgrowth of gold nanorods, all taking place while the nanorods are embedded in mesoporous SiO2 shells (AuNRs@meso-SiO2). Heating of the AuNRs@meso-SiO2 in methanol with HCl resulted in reproducible oxidation of the AuNRs by dissolved O2, specifically at the rod ends, enabling precise control over the aspect ratio of the rods. The etched-AuNRs@meso-SiO2 were used as a template for the overgrowth of a second metal (Ag, Pd, and Pt), yielding bimetallic, core-shell structured nanorods. By varying the reaction rates of the metal deposition both smooth core-shell structures or gold nanorods covered with a dendritic overlayer could be made. This control over the morphology, including metal composition, and thus the plasmonic properties of the composite rods were measured experimentally and also confirmed by Finite-Difference Time-Domain (FDTD) calculations. The presented synthesis method gives great control over tuning over both plasmonic properties and the particle stability/affinity for specific applications

Isolation and characterization of few-layer black phosphorus

Isolation and characterization of mechanically exfoliated black phosphorus flakes with a thickness down to two single-layers is presented. A modification of the mechanical exfoliation method, which provides higher yield of atomically thin flakes than conventional mechanical exfoliation, has been developed. We present general guidelines to determine the number of layers using optical microscopy, Raman spectroscopy and transmission electron microscopy in a fast and reliable way. Moreover, we demonstrate that the exfoliated flakes are highly crystalline and that they are stable even in free-standing form through Raman spectroscopy and transmission electron microscopy measurements. A strong thickness dependence of the band structure is found by density functional theory calculations. The exciton binding energy, within an effective mass approximation, is also calculated for different number of layers. Our computational results for the optical gap are consistent with preliminary photoluminescence results on thin flakes. Finally, we study the environmental stability of black phosphorus flakes finding that the flakes are very hydrophilic and that long term exposure to air moisture etches black phosphorus away. Nonetheless, we demonstrate that the aging of the flakes is slow enough to allow fabrication of field-effect transistors with strong ambipolar behavior. Density functional theory calculations also give us insight into the water-induced changes of the structural and electronic properties of black phosphorus.Comment: 11 main figures, 7 supporting figure

Регіональні аспекти удосконалення системи управління персоналом на державній службі

У статті розкривається суть регіональних вимірів удосконалення системи управління персоналом на державній службі та висвітлюється досвід Управління державної служби Головдержслужби України в Миколаївській області на шляху до прозорості влади і залучення громадськості до державотворення.The article reveals the essence of regional measurements of improvement the HR Management system in the civil service and reports the experience of the Office of Civil Service of The Main Department of Civil Service of Ukraine in the Mykolaiv region towards transparency in government and public involvement in the nation