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Learn about the nonmetal elements such as the noble gases and hydrogen.

Although diatomic nitrogen is famously inert, a variety of transition metals can bind to it through a process termed backbonding. As the nitrogen weakly shares its own electrons, some electrons from the metal reach back out to it. Nonmetals would not seem to have the capacity for this type of bonding, but now Légaré et al. show that conventionally electron-deficient boron can be coaxed into it (see the Perspective by Broere and Holland). The authors treated boron-based precursors with potassium under a nitrogen atmosphere to produce several compounds with sandwiched dinitrogen between two boron centers in reduced motifs reminiscent of metal complexes. Science , this issue p. 896 ; see also p. 871 A boron compound reduced by potassium can bind N 2 in a motif reminiscent of transition metal complexes. Currently, the only compounds known to support fixation and functionalization of dinitrogen (N 2 ) under nonmatrix conditions are based on metals. Here we present the observation of N 2 binding and reduction by a nonmetal, specifically a dicoordinate borylene. Depending on the reaction conditions under which potassium graphite is introduced as a reductant, N 2 binding to two borylene units results in either neutral (B 2 N 2 ) or dianionic ([B 2 N 2 ] 2– ) products that can be interconverted by respective exposure to further reductant or to air. The 15 N isotopologues of the neutral and dianionic molecules were prepared with 15 N-labeled dinitrogen, allowing observation of the nitrogen nuclei by 15 N nuclear magnetic resonance spectroscopy. Protonation of the dianionic compound with distilled water furnishes a diradical product with a central hydrazido B 2 N 2 H 2 unit. All three products were characterized spectroscopically and crystallographically.

The ability to tailor the morphology of semiconductors in order to obtain the desired properties will add new dimension to the fundamental physics, materials science and engineering of these materials for a variety of applications. Due to its high absorptance, Black Silicon presents new opportunities for applications in energy, healthcare and thermal management.

DNA sequencing: enter the graphene nanopore Atomically thin layers of graphite — known as graphene — are highly electronically conducting across the plane of the material. Now researchers from Harvard University and the Massachusetts Institute of Technology show that, when used as a membrane separating two liquid reservoirs, graphene is strongly ionically insulating, while its in-plane electronic properties are strongly dependent on the inter-facial environment. The membrane prevents ions and water from flowing through it, but can attract various ions and other molecules to its two atomically close surfaces. A variety of analytical applications may result. For instance, the authors show that by drilling pores a few nanometres in diameter into these 'trans-electrode' membranes, it is possible to thread a long DNA molecule through the graphene nanopore. The DNA blocks the flow of ions, resulting in a characteristic electrical signal reflecting the size and conformation of the molecule. Such a system has potential as the basis of devices that could significantly reduce the cost of DNA sequencing. Graphene is highly electronically conducting across the plane of the material. These authors show that a graphene membrane separating two ionic solutions in electrical contact is strongly ionically insulating despite being atomically thin and has in-plane electronic properties dependent on the interfacial environment. Numerical modelling reveals that very high spatial resolution is possible using this system, and the researchers propose that drilled membranes could form the basis of DNA sequencing devices. Isolated, atomically thin conducting membranes of graphite, called graphene, have recently been the subject of intense research with the hope that practical applications in fields ranging from electronics to energy science will emerge 1 . The atomic thinness, stability and electrical sensitivity of graphene motivated us to investigate the potential use of graphene membranes and graphene nanopores to characterize single molecules of DNA in ionic solution. Here we show that when immersed in an ionic solution, a layer of graphene becomes a new electrochemical structure that we call a trans-electrode. The trans-electrode’s unique properties are the consequence of the atomic-scale proximity of its two opposing liquid–solid interfaces together with graphene’s well known in-plane conductivity. We show that several trans-electrode properties are revealed by ionic conductance measurements on a graphene membrane that separates two aqueous ionic solutions. Although our membranes are only one to two atomic layers 2 , 3 thick, we find they are remarkable ionic insulators with a very small stable conductance that depends on the ion species in solution. Electrical measurements on graphene membranes in which a single nanopore has been drilled show that the membrane’s effective insulating thickness is less than one nanometre. This small effective thickness makes graphene an ideal substrate for very high resolution, high throughput nanopore-based single-molecule detectors. The sensitivity of graphene’s in-plane electronic conductivity to its immediate surface environment and trans-membrane solution potentials will offer new insights into atomic surface processes and sensor development opportunities.

The search for electrolyte materials with high oxygen conductivities is a key step toward reducing the operation temperature of fuel cells, which is currently above 700°C. We report a high lateral ionic conductivity, showing up to eight orders of magnitude enhancement near room temperature, in yttria-stabilized zirconia (YSZ)/strontium titanate epitaxial heterostructures. The enhancement of the conductivity is observed, along with a YSZ layer thickness-independent conductance, showing that it is an interface process. We propose that the atomic reconstruction at the interface between highly dissimilar structures (such as fluorite and perovskite) provides both a large number of carriers and a high-mobility plane, yielding colossal values of the ionic conductivity.

Phosphorus has always been both a curse and a blessing. On the one hand, it is essential for all life forms and cannot be replaced by anything. On the other hand, wastewater treatment aims to minimize phosphorus concentrations in wastewater in order to minimize its discharge into rivers and lakes, where eutrophication caused by high phosphorus concentrations would lead to excessive plant growth. Phosphorus is extracted from rock phosphate deposits, which are finite and non-renewable. And as the issue of resource conservation is the focus of attention worldwide, phosphorus must be used sustainably. This includes recycling of secondary phosphates, efficient extraction and treatment of raw phosphate as well as its efficient use.

Advanced oxidation process (AOP) is a versatile photocatalytic approach to degrade various environmental pollutants. Among many photocatalysts used in AOP such as ZnO, TiO2, ZrO2, ZnS, CdS; TiO2 is the most widely adopted semiconductor material. TiO2 is a wide band gap material and absorb in UV spectrum which is a narrow region in the sun light. This benchmark makes it a less efficient photocatalyst under sunlight irradiation. To enhance the photocatalytic efficiency, the absorption band of photocatalyst should be modified in such a way that it leads to maximum absorption in the solar spectrum. The doping of nonmetals such as N, C, P and S etc. shift the band edge of the semiconductors towards the visible region and thus increases the photon absorption which successively enhances the photocatalytic efficiency. In this review, we have focused on effect of nonmetal doping on the properties and photocatalytic activity of the TiO2. Influence of various aspects such as synthesis procedure, doping source, concentration of dopant, calcination etc. are also explored towards alteration in properties and photocatalytic efficiency of nonmetals doped TiO2.

Efficient flexible energy storage systems have received tremendous attention due to their enormous potential applications in self-powering portable electronic devices, including roll-up displays, electronic paper, and “smart” garments outfitted with piezoelectric patches to harvest energy from body movement. Unfortunately, the further development of these technologies faces great challenges due to a lack of ideal electrode materials with the right electrochemical behavior and mechanical properties. MXenes, which exhibit outstanding mechanical properties, hydrophilic surfaces, and high conductivities, have been identified as promising electrode material candidates. In this work, taking 2D transition metal carbides (TMCs) as representatives, we systematically explored several influencing factors, including transition metal species, layer thickness, functional group, and strain on their mechanical properties (e.g., stiffness, flexibility, and strength) and their electrochemical properties (e.g., ionic mobility, equilibrium voltage, and theoretical capacity). Considering potential charge-transfer polarization, we employed a charged electrode model to simulate ionic mobility and found that ionic mobility has a unique dependence on the surface atomic configuration influenced by bond length, valence electron number, functional groups, and strain. Under multiaxial loadings, electrical conductivity, high ionic mobility, low equilibrium voltage with good stability, excellent flexibility, and high theoretical capacity indicate that the bare 2D TMCs have potential to be ideal flexible anode materials, whereas the surface functionalization degrades the transport mobility and increases the equilibrium voltage due to bonding between the nonmetals and Li. These results provide valuable insights for experimental explorations of flexible anode candidates based on 2D TMCs.

The electronic properties of n- and p-type semiconductors using nonmetals (H, B, C, N, O, Si, P, Se, F, Cl, Br, and I) to substitute sulfur in the TcS2 monolayer were investigated using first-principles methods based on the density functional theory. The H-, B-, C-, N-, Si-, and P-doped systems were p-type, whereas the F-doped systems were n-type semiconductors. Numerical results showed that these nonmetals induced magnetic properties through the dopant p orbital and neighboring Tc atom d orbitals. H-, B-, N-, P-, and F-doped systems exhibited semiconducting magnetic nanomaterial features, whereas Cl-, Br-, and I-doped systems exhibited half-metallic magnetic features. The formation energy of the C-doped system was the lowest followed by the O-doped system, compared to that of the other examined systems. Under Tc-rich growth conditions, the preparation of nonmetal-doped TcS2 was facile and stable because of its negative impurity formation energy. A more significant change was observed at the band edges of the doped systems compared to the pristine TcS2 monolayer. These results provided fundamental insights into the doped TcS2 monolayer for application as photocatalysts and spintronic, optoelectronic, and electronic devices.