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Membrane-based separation is an appealing solution to mitigate CO2 emission sustainably due to its energy efficiency and environmental friendliness. Attributed to its excellent separation endowed by nanomaterial incorporation, nanocomposite membrane is rigorously developed. This study explored the feasibility of boron nitride (BN) embedment and changes to formation mechanism of ultrathin selective layer of thin film nanocomposite (TFN) are investigated. The effects of amine-functionalization on nanosheet-polymer interaction and CO2 separation performance are also identified. Participation of nanosheets during interfacial polymerization reduced the crosslinking of selective layer, hence, improved TFN permeance while the formation of contorted diffusion paths by the nanosheets favors transport of small gases. Amine-functionalization enhanced the nanosheet-polymer interaction and elevated the membrane affinity towards CO2 which led to enhanced CO2 selectivity. The best TFN prepared in this study exhibited 37% and 20% increment in permeability and selectivity, respectively with respect to neat thin film composite (TFC). It is found that the CO2 separation performance of BN incorporated TFN is on par with many non-porous nanosheet-incorporated TFNs reported in literatures. The transport and barrier effects of BN and functionalized BN are discussed in detail to provide further insights into the development of commercially attractive CO2 selective TFN membranes.

A fluorescent dye-labeled DNA probe was adsorbed and quenched on the monolayer of RuO2 nanosheets. Significant fluorescent recovery was observed upon the addition of complementary DNA due to desorption of the probe from the surface of the RuO2 nanosheet through duplex formation. The efficiency of fluorescence recovery was higher than that for graphene oxide, which was known as a quencher-free platform for the detection of nucleic acids in a homogeneous solution.

Membrane-based separation is an appealing solution to mitigate CO

Two‐dimensional (2D) transition metal dichalcogenides (TMDCs) with unique electrical properties are fascinating materials used for future electronics. However, the strong Fermi level pinning effect at the interface of TMDCs and metal electrodes always leads to high contact resistance, which seriously hinders their application in 2D electronics. One effective way to overcome this is to use metallic TMDCs or transferred metal electrodes as van der Waals (vdW) contacts. Alternatively, using highly conductive doped TMDCs will have a profound impact on the contact engineering of 2D electronics. Here, a novel chemical vapor deposition (CVD) using mixed molten salts is established for vapor–liquid–solid growth of high‐quality rhenium (Re) and vanadium (V) doped TMDC monolayers with high controllability and reproducibility. A tunable semiconductor to metal transition is observed in the Re‐ and V‐doped TMDCs. Electrical conductivity increases up to a factor of 108 in the degenerate V‐doped WS2 and WSe2. Using V‐doped WSe2 as vdW contact, the on‐state current and on/off ratio of WSe2‐based field‐effect transistors have been substantially improved (from ≈10–8 to 10–5 A; ≈104 to 108), compared to metal contacts. Future studies on lateral contacts and interconnects using doped TMDCs will pave the way for 2D integrated circuits and flexible electronics., A chemical vapor deposition method using mixed molten salts is established for vapor–liquid–solid growth of Re‐ and V‐doped transition metal dichalcogenide (TMDC) monolayers. Tunable semiconductor to metal transition is observed in the as‐grown Re‐ and V‐doped TMDC monolayers. Using heavily V‐doped WSe2 as van der Waals contact, the performance of WSe2‐based field‐effect transistors is improved by 1–3 orders of magnitude compared to Au and Pd.

The usage of molten salts, e.g., Na2MoO4 and Na2WO4, has shown great success in the growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). In comparison with the halide salt (i.e., NaCl, NaBr, KI)-assisted growth (Salt 1.0), the molten salt-assisted vapor-liquid-solid (VLS) growth technique (Salt 2.0) has improved the reproducibility, efficiency and scalability of synthesizing 2D TMDCs. However, the growth of large-area MoSe2 and WTe2 is still quite challenging with the use Salt 2.0 technique. In this study, a renewed Salt 2.0 technique using mixed salts (e.g., Na2MoO4-Na2SeO3 and Na2WO4-Na2TeO3) is developed for the enhanced CVD growth of 2D MoSe2 and WTe2 crystals with large grain size and yield. Continuous monolayer MoSe2 film with grain size of 100-250 {\mu}m or isolated flakes up to ~ 450 {\mu}m is grown on a halved 2-inch SiO2/Si wafer. Our study further confirms the synergistic effect of Na+ and SeO32- in the enhanced CVD growth of wafer-scale monolayer MoSe2 film. And thus, the addition of Na2SeO3 and Na2TeO3 into the transition metal salts could be a general strategy for the enhanced CVD growth of many other 2D selenides and tellurides., Comment: 35 pages, 11 figures and 1 table

A fluorescent dye-labeled DNA probe was adsorbed and quenched on the monolayer of RuO

A new strategy using mixed salts for chemical vapor deposition of tunable Re‐ and V‐doped 2D transition metal dichalcogenides (TMDCs) is realized by Shisheng Li, Takaaki Taniguchi, and co‐workers, as described in article number 2004438. By applying the highly conductive V‐doped WSe(2) as van der Waals contacts for 2D WSe(2) based field‐effect transistor, the on‐state current and on/off ratio are substantially improved, compared to the metal contacts. [Image: see text]

Vapor transportation is the core process in growing transition-metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). One inevitable problem is the spatial inhomogeneity of the vapors. The non-stoichiometric supply of transition-metal precursors and chalcogen leads to poor control in products' location, morphology, crystallinity, uniformity and batch to batch reproducibility. While vapor-liquid-solid (VLS) growth involves molten precursors at the growth temperatures higher than their melting points. The liquid sodium molybdate can precipitate solid MoS2 monolayers when saturated with sulfur vapor. Taking advantage of the VLS growth, we achieved three kinds of important achievements: (a) 4-inch-wafer-scale uniform growth of MoS2 flakes on SiO2/Si substrates, (b) 2-inch-wafer-scale growth of continuous MoS2 film with a grain size exceeding 100 um on sapphire substrates, and (c) pattern (site-controlled) growth of MoS2 flakes and film. We clarified that the VLS growth thus pave the new way for the high-efficient, scalable synthesis of two-dimensional TMDC monolayers., Comment: 30 pages, 10 figures

International audience; Long poly-diacetylene chains are excellent candidates for planar, on-surface synthesizedmolecular electronic wires. Since hexagonal-Boron Nitride (h-BN) was identified as the bestavailable atomically flat insulator for the deposition of poly-diacetylene precursors, we demonstratethe polymerization patterns and rate on it under UV-light irradiation, with subsequent polymeridentification by atomic force microscopy. The results on h-BN indicate self-sensitization whichyields blocks comprised of several polymers, unlike on the well-studied graphite/diacetylene system,where the polymers are always isolated. In addition, the photo-polymerization proceeds at least170 times faster on h-BN, where it also results in longer polymers. Both effects are explained bythe h-BN bandgap, which is larger than the diacetylene electronic excitation energy, thus allowingthe transfer of excess energy absorbed by polymerized wires to adjacent monomers, triggeringtheir polymerization. This work sets the stage for conductance measurements of single molecularpoly-diacetylene wires on h-BN.

We have developed a new synthesis method that includes a chemical vapor deposition process in a chamber settled in organic liquid, and applied its nonequilibrium reaction field to the development of novel carbon nanomaterials. In the synthesis at 1110–1120 K, using graphene oxide as a catalyst support, iron acetate and cobalt acetate as catalyst precursors, and 2-propanol as a carbon source as well as the organic liquid, we succeeded to create carbon nanofiber composed of novel pot-shaped units, named carbon nanopot. A carbon nanopot has a complex and regular nanostructure consisting of several parts made of different layer numbers of graphene and a deep hollow space. Dense graphene edges, hydroxylated presumably, are localized around its closed end. The typical size of a carbon nanopot was 20–40 nm in outer diameter, 5–30 nm in inner diameter, and 100–200 nm in length. A growth model of carbon nanopot and its applications are proposed.

Chemical vapor deposition (CVD) of two-dimensional (2D) materials such as monolayer MoS2 typically involves the conversion of vapor-phase precursors to a solid product in a process that may be described as a vapor-solid-solid (VSS) mode. Here, we report the first demonstration of vapor-liquid-solid (VLS) growth of monolayer MoS2 yielding highly crystalline ribbon-shaped structures with a width of a few tens of nanometers to a few micrometers. The VLS growth mode is triggered by the reaction between molybdenum oxide and sodium chloride, which results in the formation of molten Na-Mo-O droplets. These droplets mediate the growth of MoS2 ribbons in the "crawling mode" when saturated with sulfur on a crystalline substrate. Our growth yields straight and kinked ribbons with a locally well-defined orientation, reflecting the regular horizontal motion of the liquid droplets during growth. Using atomic-resolution scanning transmission electron microscopy (STEM) and second harmonic generation (SHG) microscopy, we show that the ribbons are homoepitaxially on monolayer MoS2 surface with predominantly 2H- or 3R-type stacking. These findings pave the way to novel devices with structures of mixed dimensionalities., Comment: 40 pages, 19 figures

Exfoliation of layered materials into ultrathin nanosheets introduces a new cost-effective and environmentally safe fabrication method for novel nanostructured devices. In the present study, we have developed for the first time inorganic oxide nanosheets with near-infrared (NIR) luminescence properties. KLa1−xNdxNb2O7 (x=0.025, 0.05, 0.1, 0.2, or 0.3) powders obtained by a solid state reaction were exfoliated into single-layer metal oxide nanosheets with approximately 1.7 nm thickness by osmotic swelling with tetrabutylammonium cations, followed by the protonation of KLa1−xNdxNb2O7. We observed strong coupling of high-energy OH vibration with the Nd3+ energy levels upon protonation and exfoliation steps because of the extremely thin nature of oxide nanosheet-layers. Colloidal oxide nanosheets with an optimized Nd-doping concentration yielded detectable NIR luminescence due to 4F3/2–4I11/2 (Nd3+) radiative transitions, which opens possible application of these oxide nanosheets as bioimaging probes and bioanalytical sensors.

CaFe2O4 (p-type) and ZnO (n-type) electrodes were prepared for photoelectrochemical hydrogen production from water. The CaFe2O4 electrode showed photo-reduction current in 0.1 M NaOH aqueous solution at potentials more negative than +0.31 V vs. Ag/AgCl, while ZnO showed photo-oxidation at potentials more positive than −0.71 V vs. Ag/AgCl. Connecting the both electrodes under UV-light illumination, the open-circuit voltage between the electrodes was 0.82 V, and hydrogen gas was generated from the side of the CaFe2O4 electrode without applying an external voltage. The gas generation continued for 4 days at least. In addition, the hydrogen was generated even under a reverse bias (−0.1 V) vs. CaFe2O4 electrode.

Nanocrystalline zirconia (ZrO 2 ) powders doped with 0.5 up to 5 mol% europium (Eu 3+) were prepared by hydrothermal process using ZrCl 4 and EuCl 3 .6H 2 O as starting materials. Optical emission and vibrational properties of as-prepared and calcined samples were investigated by phonon sideband (PSB), Fourier transform infrared (FT-IR) and photoluminescence spectroscopy as well as lifetime measurements. We found that the doping degree had a strong effect on the crystalline phase, m- and t-ZrO 2 , of the host material, which also influenced on its shape and intensity of the PSB spectra. Residual water in the as-prepared samples indicated by FT-IR spectra induced water relating vibrations in the PSB spectra. The obtained PSB were compared with the peaks in the recorded FT-IR spectra and related to the vibrational modes of m- and t-ZrO 2 .

We report an effective method for the synthesis of hydroxyapatite whiskers with sharp faceted hexagonal shape employing a low temperature (90 °C) hydrothermal route with calcium nitrate tetrahydrate, diammonium phosphate and urea as starting materials. The key parameters of the synthesis process i.e. duration, temperature cycle of the treatment and starting pH value are carefully varied and the end products are investigated using powder X-ray diffraction (XRD), Raman-scattering, infrared spectroscopy (IR), elemental analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), electron diffraction (ED), and high-resolution TEM (HRTEM) in order to find the optimal reaction conditions that lead to the desired hexagonal morphology of HA whiskers. The results demonstrate that gradual and greater increase in solution pH during the hydrothermal process favors large quantity of the single-crystalline hydroxyapatite whiskers with well defined hexagonal morphology.

Folding dynamics are ubiquitously involved in controlling the multivariate functions of RNAs. While the high thermodynamic stabilities of some RNAs favor purely native states at equilibrium, it is unclear whether weakly stable RNAs exist in random, partially folded states or sample well-defined, globally folded conformations. Using a folding assay that precisely tracks the formation of native aminoacylable tRNA, we show that the folding of a weakly stable human mitochondrial (hmt) leucine tRNA is hierarchical with a distinct kinetic folding intermediate. The stabilities of the native and intermediate conformers are separated by only about 1.2 kcal/mol, and the species are readily interconvertible. Comparison of folding dynamics between unmodified and fully modified tRNAs reveals that post-transcriptional modifications produce a more constrained native structure that does not sample intermediate conformations. These structural dynamics may thus be crucial for recognition by some modifying enzymes in vivo, especially those targeting the globular core region, by allowing access to pretransition state conformers. Reduced conformational sampling of the native, modified tRNAs could then permit improved performance in downstream processes of translation. More generally, weak stabilities of small RNAs that fold in the absence of chaperone proteins may facilitate conformational switching that is central to biological function.

Understanding the chemical and physical properties of metal/graphene oxide (M/GO) interfaces is important when GO is used in electronic and electrochemical devices because the metal layer must be firmly attached to GO. Here, permeation of metal from the surface into GO paper bulk at the M/GO interface was observed at room temperature for metals such as Cu, Ag, Ni, Au and Pt. Cu, Ag and Ni quickly permeated GO as ions into the bulk under humid conditions. At first, these metals changed to hydrated ions as a result of redox reactions (with reduction of GO) at the surface and then permeated the interlayers. Au and Pt were observed to permeate GO as atoms into the GO bulk at room temperature, although the permeation rates were low. These surprising results are considered to be due to the presence of many defects and/or edges with oxygenated groups in the GO paper.

Deciphering the genetic code is a fundamental process in all living organisms. In many bacteria, AUA codons are deciphered by tRNA(Ile2) bearing lysidine (L) at the wobble position. L is a modified cytidine introduced post-transcriptionally by tRNA(Ile)-lysidine synthetase (TilS). Some bacteria, including Mycoplasma mobile, do not carry the tilS gene, indicating that they have established a different system to decode AUA codons. In this study, tRNA(Ile2) has been isolated from M. mobile and was found to contain a UAU anticodon without any modification. Mycoplasma mobile isoleucyl-tRNA synthetase (IleRS) recognized the UAU anticodon, whereas Escherichia coli IleRS did not efficiently aminoacylate tRNA(Ile2)(UAU). In M. mobile IleRS, a single Arg residue at position 865 was critical for specificity for the UAU anticodon and, when the corresponding site (W905) in E. coli IleRS was substituted with Arg, the W905R mutant efficiently aminoacylated tRNA with UAU anticodon. Mycoplasma mobile tRNA(Ile2) cannot distinguish between AUA and AUG codon on E. coli ribosome. However, on M. mobile ribosome, M. mobile tRNA(Ile2)(UAU) specifically recognized AUA codon, and not AUG codon, suggesting M. mobile ribosome has a property that prevents misreading of AUG codon. These findings provide an insight into the evolutionary reorganization of the AUA decoding system.

Ti2O52− nanosheets were successfully synthesized using a solution process under mild conditions. Concentrated nanosheet solutions (mass production) were easily obtained by the addition of sodium dodecyl sulfate (SDS). A drastic and specific enhancement of the photoluminescence of Eu3+ by energy transfer from the nanosheets occurred in the solution state.

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