Electrochemical Formation of Germanene: pH 4.5

Germanene is a single layer allotrope of Ge, with a honeycomb structure similar to graphene. This report concerns the electrochemical formation of germanene in a pH 4.5 solution. The studies were performed using in situ Electrochemical Scanning Tunneling Microscopy (EC-STM), voltammetry, coulometry, surface X-ray diffraction (SXRD) and Raman spectroscopy to study germanene electrodeposition on Au(111) terraces. The deposition of Ge is kinetically slow and stops after 2–3 monolayers. EC-STM revealed a honeycomb (HC) structure with a rhombic unit cell, 0.44 ± 0.02 nm on a side, very close to that predicted for germanene in the literature. Ideally the HC structure is a continuous sheet, with six Ge atoms around each hole. However, only small domains, surrounded by defects, of this structure were observed in this study. The small coherence length and multiple rotations domains made direct observation with surface X-ray diffraction difficult. Raman spectroscopy was used to investigate the multi-layer Ge deposits. A peak near 290 cm^(−1), predicted to correspond to germanene, was observed on one particular area of the sample, while the rest resembled amorphous germanium. Electrochemical studies of germanene showed limited stability when exposed to oxygen

Phylogenetic Distribution of CRISPR-Cas Systems in Antibiotic-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is an antibiotic-refractory pathogen with a large genome and extensive genotypic diversity. Historically, P. aeruginosa has been a major model system for understanding the molecular mechanisms underlying type I clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated protein (CRISPR-Cas)-based bacterial immune system function. However, little information on the phylogenetic distribution and potential role of these CRISPR-Cas systems in molding the P. aeruginosa accessory genome and antibiotic resistance elements is known. Computational approaches were used to identify and characterize CRISPR-Cas systems within 672 genomes, and in the process, we identified a previously unreported and putatively mobile type I-C P. aeruginosa CRISPR-Cas system. Furthermore, genomes harboring noninhibited type I-F and I-E CRISPR-Cas systems were on average ~300 kb smaller than those without a CRISPR-Cas system. In silico analysis demonstrated that the accessory genome (n = 22,036 genes) harbored the majority of identified CRISPR-Cas targets. We also assembled a global spacer library that aided the identification of difficult-to-characterize mobile genetic elements within next-generation sequencing (NGS) data and allowed CRISPR typing of a majority of P. aeruginosa strains. In summary, our analysis demonstrated that CRISPR-Cas systems play an important role in shaping the accessory genomes of globally distributed P. aeruginosa isolates

Investigations into the Formation of Germanene Using Electrochemical Atomic Layer Deposition (E-ALD)

This paper will discuss possible formation of germanene electrochemically. Germanene should be a single layer allotrope of Ge. The techniques of in-situ electrochemical STM (EC-STM), voltammetry, coulometry, and micro-Raman have been used to investigate the electrochemical formation of germanene. Studies on Au(111) show that the initial deposition of Ge is kinetically slow and somewhat unstable, whereas the self-limited layer of Ge is stable and shows atomic distances of about 0.44 nm ± 0.02 nm. Micro-Raman was performed on Ge nanofilms, but only displayed a shift near 290 cm^(-1) in one area. Given the STM results, it appears that the coherence of the germanene domains will need to be increased in order to more consistently produce the Raman signal. The data presented suggest that germanene has been formed electrochemically, although only as a minority species

Investigations into the Formation of Germanene Using Electrochemical Atomic Layer Deposition (E-ALD)

This paper will discuss possible formation of germanene electrochemically. Germanene should be a single layer allotrope of Ge. The techniques of in-situ electrochemical STM (EC-STM), voltammetry, coulometry, and micro-Raman have been used to investigate the electrochemical formation of germanene. Studies on Au(111) show that the initial deposition of Ge is kinetically slow and somewhat unstable, whereas the self-limited layer of Ge is stable and shows atomic distances of about 0.44 nm ± 0.02 nm. Micro-Raman was performed on Ge nanofilms, but only displayed a shift near 290 cm^(-1) in one area. Given the STM results, it appears that the coherence of the germanene domains will need to be increased in order to more consistently produce the Raman signal. The data presented suggest that germanene has been formed electrochemically, although only as a minority species