The influence of deposits from copper mining and smelting combine Bor on the vegetation of riverside of the river Timok (Eastern Serbia)

The quantity of tail and other harmful products of RTB-Bor (Copper mining and smelting combine Bor) have significantly increased since the mid twentieth century, and were carried into the lower stream of the river Timok, mainly through the Borska River. Flooding the surrounding areas and producing thick deposits of substratum with the extreme characteristics caused the devastation and degradation of the autochthonous plant communities and large areas of arable land. This caused the appearance of new, atypical species such as Betula pendula Roth, Robinia pseudoacacia, Amorpha fruticosa, Calamagrostis epigeios, Erigeron Canadensis and other species in the devastated and degraded community of Salici-Populetum albae in the areas of Tamnic, Brusnik and Bracevac villages, and they have significantly changed typical floristic composition of the community.nul

The influence of deposits from copper mining and smelting combine Bor on the vegetation of riverside of the river Timok (Eastern Serbia)

The quantity of tail and other harmful products of RTB-Bor (Copper mining and smelting combine Bor) have significantly increased since the mid twentieth century, and were carried into the lower stream of the river Timok, mainly through the Borska River. Flooding the surrounding areas and producing thick deposits of substratum with the extreme characteristics caused the devastation and degradation of the autochthonous plant communities and large areas of arable land. This caused the appearance of new, atypical species such as Betula pendula Roth, Robinia pseudoacacia, Amorpha fruticosa, Calamagrostis epigeios, Erigeron Canadensis and other species in the devastated and degraded community of Salici-Populetum albae in the areas of Tamnic, Brusnik and Bracevac villages, and they have significantly changed typical floristic composition of the community.nul

DNA Sequencing with Single-Stranded DNA Rectification in a Nanogap Gated by N‑Terminated Carbon Nanotube Electrodes

Fast, reliable, and inexpensive DNA sequencing is an important pursuit in healthcare, especially in personalized medicine with possible deep societal impacts. Despite significant progress in various nanopore-based sequencing configurations, challenges that remain in resolution and chromosome-size-long readout call for new approaches. Here we found strong rectification in the transversal current during single-stranded DNA translocation through a nanopore with side-embedded N-terminated carbon nanotube electrodes. Employing density functional theory and nonequilibrium Green’s function formalisms, we show that the rectifying ratio (response to square pulses of alternating bias) bears high nucleobase specificity. Rectification arises because of bias-dependent resistance asymmetry on the deoxyribonucleotide−electrode interfaces. The asymmetry induces molecular charging and highest occupied molecular orbital pinning to the electrochemical potential of one of the electrodes, assisted by an in-gap electric-field effect caused by dipoles at the terminated electrode ends. We propose the rectifying ratio, due to its order-of-magnitude-difference nucleobase selectivity and robustness to electrode-molecule orientation, as a promising readout quantifier for single-base resolution and chromosome-size-long single-read DNA sequencing. The proposed configurations are within experimental reach from the viewpoint of both nanofabrication and small current measurement

Field Effect and Local Gating in Nitrogen‐Terminated Nanopores (NtNP) and Nanogaps (NtNG) in Graphene

Functionalization of electrodes is a wide‐used strategy in various applications ranging from single‐molecule sensing and protein sequencing, to ion trapping, to desalination. We demonstrate, employing non‐equilibrium Green′s function formalism combined with density functional theory, that single‐species (N, H, S, Cl, F) termination of graphene nanogap electrodes results in a strong in‐gap electrostatic field, induced by species‐dependent dipoles formed at the electrode ends. Consequently, the field increases or decreases electronic transport through a molecule (benzene) placed in the nanogap by shifting molecular levels by almost 2 eV in respect to the electrode Fermi level via a field effect akin to the one used for field‐effect transistors. We also observed the local gating in graphene nanopores terminated with different single‐species atoms. Nitrogen‐terminated nanogaps (NtNGs) and nanopores (NtNPs) show the strongest effect. The in‐gap potential can be transformed from a plateau‐like to a saddle‐like shape by tailoring NtNG and NtNP size and termination type. In particular, the saddle‐like potential is applicable in single‐ion trapping and desalination devices.The accepted, peer-reviewed version: [https://cer.ihtm.bg.ac.rs/handle/123456789/4048]The submitted, pre-peer reviewed version: [https://cer.ihtm.bg.ac.rs/handle/123456789/4049

Fast photoluminescence quenching in thin films of 4,4 '-bis(2,2-diphenylvinyl)-1,1 '-biphenyl exposed to air

The photoluminescence (PL) quenching mechanism of UV light and air-exposed amorphous thin films of 4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl (DPVBi), a well-known hole-transport material used in organic light-emitting diodes, is studied. Thin films of DPVBi are stable when exposed to UV light in vacuum but tend to degrade if oxygen is present simultaneously. This is evident from the changes in UV-vis absorption spectra of the latter, showing that degradation rate of DPVBi films is linearly proportional to both oxygen concentration and UV light intensity. Mass spectrometry study of such films revealed a number of different oxygen-containing molecules and fragments of DPVBi thus confirming apparent photo-oxidation process. Also, DFT study of molecular DPVBi with and without oxygen was carried out, the IR spectra calculated for the lowest energy molecules found and the results are compared with the experiment. The most sensitive to photo-oxidation is DPVBi photoluminescence, which decays exponentially with respect to the concentration of photo-oxidized DPVBi molecules (impurities). The PL quantum yield of DPVBi thin film drops to a half of its original value for 0.2% of the impurities present, at which point an average distance between DPVBi molecules (the donors) and photo-oxidized DPVBi species (acceptors) is an order of magnitude larger than the separation between two adjacent molecules. This implies a need for a long-range Forster energy transfer, which we rule out based on the lack of a donor-acceptor spectral overlap. The apparent discrepancy can be removed by postulating exciton self-diffusion in DPVBi thin films, for which there is supporting evidence in existing literature