Cover Picture: Recoding the Genetic Code with Selenocysteine (Angew. Chem. Int. Ed. 1/2014)

Hydrogen purification performance of a nanoporous hexagonal boron nitride membrane: molecular dynamics and first-principle simulations

Double-layer models of porous h-BN monolayers, with pores differing in size and chemistry, were employed for efficient gas separation and purification. Performance was evaluated by DFT calculations and MD simulations.

Intrinsic high water/ion selectivity of graphene oxide lamellar membranes in concentration gradient-driven diffusion

Although graphene oxide lamellar membranes (GOLMs) are effective in blocking large organic molecules and nanoparticles for nanofiltration and ultrafiltration, water desalination with GOLM is challenging, with seriously controversial results. Here, a combined experimental and molecular dynamics simulation study shows that intrinsic high water/ion selectivity of GOLM was achieved in concentration gradient-driven diffusion, showing great promise in water desalination. However, in pressure-driven filtration the salt rejection was poor. This study unveils a long-overlooked reason behind the controversy in water desalination with GOLM and further provides a fundamental understanding on the in-depth mechanism concerning the strong correlation of water/ion selectivity with the applied pressure and GO nanochannel length. Our calculations and experiments show that the applied pressure weakened the water-ion interactions in GO nanochannels and reduced their permeation selectivity, while the length of nanochannels dominated the mass transport processes and the ion selectivity. The new insights presented here may open up new opportunities for the optimization of GOLMs in this challenging area.

Accessing Drug Metabolites via Transition-Metal Catalyzed C-H Oxidation: The Liver as Synthetic Inspiration

Can classical and modern chemical C-H oxidation reactions complement biotransformation in the synthesis of drug metabolites? We have surveyed the literature in an effort to try to answer this important question of major practical significance in the pharmaceutical industry. Drug metabolites are required throughout all phases of the drug discovery and development process; however, their synthesis is still an unsolved problem. This Review, not intended to be comprehensive or historical, highlights relevant applications of chemical C-H oxidation reactions, electrochemistry and microfluidic technologies to drug templates in order to access drug metabolites, and also highlights promising reactions to this end. Where possible or appropriate, the contrast with biotransformation is drawn. In doing so, we have tried to identify gaps where they exist in the hope to spur further activity in this very important research area.

Capturing Solvation Effects at a Liquid/Nanoparticle Interface by Ab Initio Molecular Dynamics: Pt201 Immersed in Water

Solvation can substantially modify the adsorption properties of heterogeneous catalysts. Although essential for achieving realistic theoretical models, assessing such solvent effects over nanoparticles is challenging from a computational standpoint due to the complexity of those liquid/metal interfaces. This effect is investigated by ab initio molecular dynamics simulations at 350 K of a large platinum nanoparticle immersed in liquid water. The first solvation layer contains twice as much physisorbed water molecules above the terraces, than chemisorbed ones located only at edges and corners. The solvent stabilizes the binding energy of chemisorbates: 66% of the total gain comes from interactions with physisorbed molecules and 34% from the influence of bulk liquid.

Organolead Halide Perovskites for Low Operating Voltage Multilevel Resistive Switching

Organolead halide perovskites are used for low-operating-voltage multilevel resistive switching. Ag/CH3 NH3 PbI3 /Pt cells exhibit electroforming-free resistive switching at an electric field of 3.25 × 10(3) V cm(-1) for four distinguishable ON-state resistance levels. The migration of iodine interstitials and vacancies with low activation energies is responsible for the low-electric-field resistive switching via filament formation and annihilation.

Molecular Structure of Aggregated Amyloid-β: Insights from Solid-State Nuclear Magnetic Resonance

Amyloid-β (Aβ) peptides aggregate to form polymorphic amyloid fibrils and a variety of intermediate assemblies, including oligomers and protofibrils, both in vitro and in human brain tissue. Since the beginning of the 21st century, considerable progress has been made to characterize the molecular structures of Aβ aggregates. Full molecular structural models based primarily on data from measurements using solid-state nuclear magnetic resonance (ssNMR) have been developed for several in vitro Aβ fibrils and one metastable protofibril. Partial structural characterization of other aggregation intermediates has been achieved. One full structural model for fibrils derived from brain tissue has also been reported. Future work is likely to focus on additional structures from brain tissue and on further clarification of nonfibrillar Aβ aggregates.

Synthesis and evaluation of hybrid molecules targeting the vinca domain of tubulin

Some hybrids of vinca alkaloids and phomopsin A, linked by a glycine pattern, have been synthesized in one or two steps, by an insertion reaction and shown to inhibit microtubule assembly. These compounds have been elaborated in order to interact with both the "vinca site" and the "peptide site" of the vinca domain in tubulin. Two out of three hybrids are potent inhibitors of microtubules assembly and they present good cytotoxicity against different cell lines. Molecular modelling studies show that they could bind, within the vinca domain, in similar spatial regions as those of vinca and phomopsin thanks to the flexibility provided by the glycine linker used to elaborate these hybrids.

Copper-catalyzed radical coupling of 1,3-dicarbonyl compounds with terminal alkenes for the synthesis of tetracarbonyl compounds

A novel and efficient copper-catalyzed radical cross-coupling of 1,3-dicarbonyl compounds with terminal alkenes for the synthesis of tetracarbonyl compounds with a quaternary carbon atom has been developed. Mechanistically, this transformation involves the construction of two C-C bonds and two C[double bond, length as m-dash]O bonds in a one-pot process. The reaction tolerates a wide range of functional groups and proceeds under mild conditions.

Enhanced Charge Collection with Passivation Layers in Perovskite Solar Cells

The Al2 O3 passivation layer is beneficial for mesoporous TiO2 -based perovskite solar cells when it is deposited selectively on the compact TiO2 surface. Such a passivation layer suppressing surface recombination can be formed by thermal decomposition of the perovskite layer during post-annealing.

Comparative study on the spectral properties of boron clusters Bn(0/-1)(n = 38-40)

The all-boron fullerenes B40(-1) and B39(-1) discovered in recent experiments are characterized and revealed using photoelectron spectroscopy. Except for the photoelectron spectroscopy, one may identify such boron clusters with other spectroscopic techniques, such as infrared spectra and Raman spectra. Insight into the spectral properties of boron clusters is important to understand the boron clusters and find their potential applications. In this work, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are carried out to comparatively study the vibrational frequencies, infrared spectra, Raman spectra and electronic absorption spectra of boron clusters Bn(0/-1)(n = 38-40). The numerical simulations show that such boron clusters have different and meaningful spectral features. These spectral features are readily compared with future spectroscopy measurements and can be used as fingerprints to distinguish the boron clusters Bn(0/-1) with different structures (cage structure or quasi-planar structure) and with different sizes (n = 38-40).

Recent Developments in Graphene-Based Membranes: Structure, Mass-Transport Mechanism and Potential Applications

Significant achievements have been made on the development of next-generation filtration and separation membranes using graphene materials, as graphene-based membranes can afford numerous novel mass-transport properties that are not possible in state-of-art commercial membranes, making them promising in areas such as membrane separation, water desalination, proton conductors, energy storage and conversion, etc. The latest developments on understanding mass transport through graphene-based membranes, including perfect graphene lattice, nanoporous graphene and graphene oxide membranes are reviewed here in relation to their potential applications. A summary and outlook is further provided on the opportunities and challenges in this arising field. The aspects discussed may enable researchers to better understand the mass-transport mechanism and to optimize the synthesis of graphene-based membranes toward large-scale production for a wide range of applications.

2-Dimensional graphene as a route for emergence of additional dimension nanomaterials

Dimension has a different and impactful significance in the field of innovation, research and technologies. Starting from one-dimension, now, we all are moving towards 3-D visuals and try to do the things in this dimension. However, we still have some very innovative and widely applicable nanomaterials, which have tremendous potential in the form of 2-D only i.e. graphene. In this review, we have tried to incorporate the reported pathways used so far for modification of 2-D graphene sheets to make is three-dimensional. The modified graphene been applied in many fields like supercapacitors, sensors, catalysis, energy storage devices and many more. In addition, we have also incorporated the conversion of 2-D graphene to their various other dimensions like zero-, one- or three-dimensional nanostructures.

Multiscale deformations lead to high toughness and circularly polarized emission in helical nacre-like fibres

Nacre-like composites have been investigated typically in the form of coatings or free-standing sheets. They demonstrated remarkable mechanical properties and are used as ultrastrong materials but macroscale fibres with nacre-like organization can improve mechanical properties even further. The fiber form or nacre can, simplify manufacturing and offer new functional properties unknown yet for other forms of biomimetic materials. Here we demonstrate that nacre-like fibres can be produced by shear-induced self-assembly of nanoplatelets. The synergy between two structural motifs--nanoscale brick-and-mortar stacking of platelets and microscale twisting of the fibres--gives rise to high stretchability (>400%) and gravimetric toughness (640 J g(-1)). These unique mechanical properties originate from the multiscale deformation regime involving solid-state self-organization processes that lead to efficient energy dissipation. Incorporating luminescent CdTe nanowires into these fibres imparts the new property of mechanically tunable circularly polarized luminescence. The nacre-like fibres open a novel technological space for optomechanics of biomimetic composites, while their continuous spinning methodology makes scalable production realistic.

A Versatile Strategy to Synthesize Perfluoropolyether-Based Thermoplastic Fluoropolymers by Alkyne-Azide Step-Growth Polymerization

Perfluoropolyether (PFPE)-based thermoplastic fluoropolymers are synthesized by A2 + B2 step-growth polymerization between PFPE-diyne and fluorinated diazides. This versatile method allows synthesizing PFPE-based materials with tunable physicochemical properties depending on the exact nature of the fluorinated segment of the diazide precursor. Semicrystalline or amorphous materials endowed with high thermostability (≈300 °C under air) and low glass transition temperature (≈-100 °C) are obtained, as confirmed by differential scanning calorimetry, thermogravimetry, and rheometry. Step-growth polymerizations can be copper-catalyzed but also thermally activated in some cases, thus avoiding the presence of copper residues in the final materials. This strategy opens up new opportunities to easily access PFPE-based materials on an industrial scale. Furthermore, a plethora of developments can be envisioned (e.g., by adding a third trifunctional component to the formulations for the synthesis of PFPE-based elastomers).

The construction of a two-dimensional supramolecular organic framework with parallelogram pores and stepwise fluorescence enhancement

A novel single-layer two-dimensional (2D) supramolecular organic framework (SOF) with parallelogram pores has been assembled to turn on the fluorescence emission of a non-emissive building block, and the emission could be further enhanced by the aggregation of the as-prepared 2D monolayers.

Construction of a smart temperature-responsive GPx mimic based on the self-assembly of supra-amphiphiles

Glutathione peroxidase (GPx) is a major defense against hydroperoxides as a kind of seleno-enzyme that protects cells from oxidative damage. A supramolecular vesicle with controllable GPx activity and morphology has been successfully constructed by the self-assembly of supra-amphiphiles formed by host-guest recognition between cyclodextrin and adamantane derivatives. By introducing thermosensitive poly(N-isopropylacrylamide) (PNIPAM) scaffolds and the catalytic moiety selenium into adamantane and cyclodextrin, respectively, the complex of catalysis-functionalized cyclodextrin with thermosensitivity-functionalized adamantane directed the formation of a supramolecular vesicle which acted as a GPx mimic at 37 °C. The self-assembled nanoenzyme exhibited an obvious temperature responsive characteristic and high GPx-like catalytic activity promoting the reduction of hydrogen peroxide (H2O2) with glutathione (GSH) as the reducing substrate at 37 °C. However, the vesicle disassembled when the temperature decreased to 25 °C due to the transition of PNIPAM between the coil and the globule. Interestingly, the catalytic activity changed along with the transformation of morphologies. The vesicle structure self-assembled at 37 °C provided the favorable microenvironment for the enzymatic reaction, hence we successfully developed a temperature-responsive nanoenzyme model. Moreover, the catalytic activity of the thermosensitive GPx mimic exhibited excellent reversibility and typical saturation kinetics behaviour similar to a natural enzyme catalyst. It is assumed that the proposed GPx model not only has remarkable advantages such as easy functionalization and facile preparation but also provided a new way to develop intelligent responsive materials.

Novel cobalt quantum dot/graphene nanocomposites as highly efficient electrocatalysts for water splitting

A cost-effective, non-noble metal based high-performance electrocatalyst for the oxygen evolution reaction (OER) is critical to energy conversion and storage processes. Here, we report on a facile and effective in situ strategy for the synthesis of an advanced nanocomposite material that is comprised of cobalt quantum dots (Co QDs, ∼3.2 nm), uniformly dispersed on reduced graphene oxide (rGO) as a highly efficient OER electrocatalyst platform. This nanocomposite electrocatalyst afforded a mass activity of 1250 A g(-1) at a low overpotential (η) of 0.37 V, a small Tafel slope of ∼37 mV dec(-1) and a turnover frequency (TOF) of 0.188 s(-1) in 0.1 M KOH, comparing favorably with state-of-the-art RuO2, IrO2 and Pt/C catalysts. The synergy between abundant catalytically active sites through the fine dispersion of Co QDs, and enhanced electron transfer generated from the graphene resulted in first-rate electrocatalytic properties toward the OER. These merits coupled with the higher stability of the nanocomposite hold great promise for triggering breakthroughs in electrocatalysis for water splitting.

Facile synthesis of diverse transition metal oxide nanoparticles and electrochemical properties

Four diverse metal oxide nanoparticles are synthesized successfully and CoO nano-cubes show excellent electrochemical properties.

Copper-catalyzed decarboxylative stereospecific amidation of cinnamic acids with N-fluorobenzenesulfonimide

A copper-catalyzed decarboxylative coupling of cinnamic acids with N-fluorobenzenesulfonimide (NFSI), to give the substituted (E)-amination products stereospecifically, has been realized.

Preparation of macroscopic spherical porous carbons@carboxymethylcellulose sodium gel beads and application for removal of tetracycline

We report a new convenient macroscopic granular adsorbent for the removal of tetracycline from water by immobilizing porous carbons into carboxymethylcellulose sodium gel beads.

Self-assembly of nitrogen-doped carbon nanoparticles: a new ratiometric UV-vis optical sensor for the highly sensitive and selective detection of Hg2+ in aqueous solution

A novel ratiometric UV-vis optical sensor for Hg²⁺ was developed based on the self-assembly of nitrogen-doped carbon nanoparticles.

Novel aggregation-induced emission and thermally activated delayed fluorescence materials based on thianthrene-9,9′,10,10′-tetraoxide derivatives

By introducing more proportion of carbazole, the newly designed molecule 3tCzDSO2 integrates the features of AIE and TADF with extremely small ΔE_ST.

Tuning Ni nanoparticles and the acid sites of silica-alumina for liquefaction and hydrodeoxygenation of lignin to cyclic alkanes

A facile and effective method for the one-pot hydrodeoxygenation of enzymatic lignin to C₆–C₉ cycloalkanes is reported in liquid dodecane with 100 C% selectivity (approaching 50 wt% yield).

Ultrafine potassium titanate nanowires: a new Ti-based anode for sodium ion batteries

The ultrafine K₂Ti₆O₁₃nanowires growing perpendicularly to the Na⁺diffusion direction greatly shorten the Na⁺diffusion length, and thus can show high reactivity for sodium storage.

Decoration of porphyrin with tetraphenylethene: converting a fluorophore with aggregation-caused quenching to aggregation-induced emission enhancement

A new porphyrin derivative with aggregation-induced emission enhancement was synthesized via tetraphenylethene decoration and it demonstrates bright imaging ability in vitro.

Fluorescent polyvinyl alcohol films based on nitrogen and sulfur co-doped carbon dots towards white light-emitting devices

Warm white light with color coordinates of (0.40, 0.38) and CCT of 3980 K was obtained using NS-CDs and PVA.

A facile self-assembly strategy towards naphthalene diimide/graphene hybrids as high performance organic cathodes for lithium-ion batteries

A hybrid of naphthalene diimide and reduced graphene oxide (NDI–RGO) has been constructed by a facile self-assembly strategy. As the cathode material in lithium ion batteries, NDI–RGO manifests a capacity of 170 mA h g⁻¹ at 25 mA g⁻¹ for 260 cycles.