Reaction-driven restructuring of defective PtSe into ultrastable catalyst for the oxygen reduction reaction.

PtM (M = S, Se, Te) dichalcogenides are promising two-dimensional materials for electronics, optoelectronics and gas sensors due to their high air stability, tunable bandgap and high carrier mobility. However, their potential as electrocatalysts for the oxygen reduction reaction (ORR) is often underestimated due to their semiconducting properties and limited surface area from van der Waals stacking. Here we show an approach for synthesizing a highly efficient and stable ORR catalyst by restructuring defective platinum diselenide (DEF-PtSe) through electrochemical cycling in an O-saturated electrolyte.

Rare isotope-containing diamond colour centres for fundamental symmetry tests.

Detecting a non-zero electric dipole moment in a particle would unambiguously signify physics beyond the Standard Model. A potential pathway towards this is the detection of a nuclear Schiff moment, the magnitude of which is enhanced by the presence of nuclear octupole deformation. However, due to the low production rate of isotopes featuring such 'pear-shaped' nuclei, capturing, detecting and manipulating them efficiently is a crucial prerequisite.

Thermodynamics, Kinetics, and Optical Properties of Rotaxane: A First-Principles Molecular Dynamics Study.

Through molecular mechanics using the force field along with the quantum dynamical aspect of mechanically interlocked compounds, rotaxanes (defined as macromolecular rings that are threaded on a dumbbell-shaped axle molecule) are investigated with advanced quantum mechanical methods, including the atom-centered density matrix propagation simulation technique, at different temperatures like 300, 500, 700, 900, 2000, and 2500 K for 1.2 ps. molecular dynamics simulation is carried out.

Synergistic Steric and Electronic Effects on the Photoredox Catalysis by a Multivariate Library of Titania Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) that display photoredox activity are attractive materials for sustainable photocatalysis. The ability to tune both their pore sizes and electronic structures based solely on the choice of the building blocks makes them amenable for systematic studies based on physical organic and reticular chemistry principles with high degrees of synthetic control. Here, we present a library of eleven isoreticular and multivariate (MTV) photoredox-active MOFs, UCFMOF-, and UCFMTV--% with a formula TiO[], where the links are linear oligo--arylene dicarboxylates with number of -arylene rings and mol% of multivariate links containing electron-donating groups (EDGs).

Relativistic quantum calculations to understand the contribution of f-type atomic orbitals and chemical bonding of actinides with organic ligands.

The nuclear waste problem is one of the main interests of rare earth and actinide element chemistry. Studies of actinide-containing compounds are at the frontier of the applications of current theoretical methods due to the need to consider relativistic effects and approximations to the Dirac equation in them. Here, we employ four-component relativistic quantum calculations and scalar approximations to understand the contribution of f-type atomic orbitals in the chemical bonding of actinides (Ac) to organic ligands.

Multi-dimensional designer catalysts for negative emissions science (NES): bridging the gap between synthesis, simulations, and analysis.

Negative emissions technologies will play a critical role in limiting global warming to sustainable levels. Electrocatalytic and/or photocatalytic CO reduction will likely play an important role in this field moving forward, but efficient, selective catalyst materials are needed to enable the widespread adoption of these processes. The rational design of such materials is highly challenging, however, due to the complexity of the reactions involved as well as the large number of structural variables which can influence behavior at heterogeneous interfaces.

Nernstian Li intercalation into few-layer graphene and its use for the determination of K co-intercalation processes.

Alkali ion intercalation is fundamental to battery technologies for a wide spectrum of potential applications that permeate our modern lifestyle, including portable electronics, electric vehicles, and the electric grid. In spite of its importance, the Nernstian nature of the charge transfer process describing lithiation of carbon has not been described previously. Here we use the ultrathin few-layer graphene (FLG) with micron-sized grains as a powerful platform for exploring intercalation and co-intercalation mechanisms of alkali ions with high versatility.

Rapidly Reversible Organic Crystalline Switch for Conversion of Heat into Mechanical Energy.

Solid-state thermoelastic behavior-a sudden exertion of an expansive or contractive physical force following a temperature change and phase transition in a solid-state compound-is rare in organic crystals, few are reversible systems, and most of these are limited to a dozen or so cycles before the crystal degrades or they reverse slowly over the course of many minutes or even hours. Comparable to thermosalience, wherein crystal phase changes induce energetic jumping, thermomorphism produces physical work via consistent and near-instantaneous predictable directional force. In this work, we show a fully reversible thermomorphic actuator that is stable at room temperature for multiple years and is capable of actuation for more than 200 cycles at near-ambient temperature.

Understanding Disorder in 2D Materials: The Case of Carbon Doping of Silicene.

We investigate the effect of lattice disorder and local correlation effects in finite and periodic silicene structures caused by carbon doping using first-principles calculations. For both finite and periodic silicene structures, the electronic properties of carbon-doped monolayers are dramatically changed by controlling the doping sites in the structures, which is related to the amount of disorder introduced in the lattice and electron-electron correlation effects. By changing the position of the carbon dopants, we found that a Mott-Anderson transition is achieved.

Impact of Surface Modification on the Lithium, Sodium, and Potassium Intercalation Efficiency and Capacity of Few-Layer Graphene Electrodes.

In a conventional lithium-ion battery (LIB), graphite forms the negative electrode or anode. Although Na is considered one of the most attractive alternatives to Li, achieving reversible Na intercalation within graphitic materials under ambient conditions remains a challenge. More efficient carbonaceous anode materials are desired for developing advanced LIBs and battery technologies.

Stabilizing polymer electrolytes in high-voltage lithium batteries.

Electrochemical cells that utilize lithium and sodium anodes are under active study for their potential to enable high-energy batteries. Liquid and solid polymer electrolytes based on ether chemistry are among the most promising choices for rechargeable lithium and sodium batteries. However, uncontrolled anionic polymerization of these electrolytes at low anode potentials and oxidative degradation at working potentials of the most interesting cathode chemistries have led to a quite concession in the field that solid-state or flexible batteries based on polymer electrolytes can only be achieved in cells based on low- or moderate-voltage cathodes.

Intercalation of first row transition metals inside covalent-organic frameworks (COFs): a strategy to fine tune the electronic properties of porous crystalline materials.

Covalent-organic frameworks (COFs) have emerged as an important class of nano-porous crystalline materials with many potential applications. They are intriguing platforms for the design of porous skeletons with special functionality at the molecular level. However, despite their extraordinary structural tunability, it is difficult to control their electronic properties, thus hindering the potential implementation in electronic devices.

Online Measurement of Glucose Consumption from HepG2 Cells Using an Integrated Bioreactor and Enzymatic Assay.

Hepatocytes help to maintain glucose homeostasis in response to a variety of signals, including pancreatic hormones such as insulin. Insulin is released from the pancreas with variable dynamics, yet the role that these play in regulating glucose metabolism in the liver is still unclear. In this study, a modular microfluidic system was developed to quantitatively measure the effect of insulin dynamics on glucose consumption by a human hepatocarcinoma cell line, HepG2.

Synthesis and Characterization of Tris-chelate Complexes for Understanding f-Orbital Bonding in Later Actinides.

An isostructural family of f-element compounds (Ce, Nd, Sm, Gd; Am, Bk, Cf) of the redox-active dioxophenoxazine ligand (DOPO; DOPO = 2,4,6,8-tetra- tert-butyl-1-oxo-1 H-phenoxazin-9-olate) was prepared. This family, of the form M(DOPO), represents the first nonaqueous isostructural series, including the later actinides berkelium and californium. The lanthanide derivatives were fully characterized using H NMR spectroscopy and SQUID magnetometry, while all species were structurally characterized by X-ray crystallography and electronic absorption spectroscopy.

Achieving Fast and Efficient K Intercalation on Ultrathin Graphene Electrodes Modified by a Li Based Solid-Electrolyte Interphase.

Advancing beyond Li-ion batteries requires translating the beneficial characteristics of Li electrodes to attractive, yet incipient, candidates such as those based on K intercalation. Here, we use ultrathin few-layer graphene (FLG) electrodes as a model interface to show a dramatic enhancement of K intercalation performance through a simple conditioning of the solid-electrolyte interphase (SEI) in a Li containing electrolyte. Unlike the substantial plating occurring in K containing electrolytes, we found that a Li based SEI enabled efficient K intercalation with discrete staging-type phase transitions observed via cyclic voltammetry at scan rates up to 100 mVs and confirmed as ion-intercalation processes through in situ Raman spectroscopy.

Reaction mechanism of the selective reduction of CO to CO by a tetraaza [CoNH] complex in the presence of protons.

The tetraaza [CoIIN4H]2+ complex (1) is remarkable for its ability to selectively reduce CO2 to CO with 45% Faradaic efficiency and a CO to H2 ratio of 3 : 2. We employ density functional theory (DFT) to determine the reasons behind the unusual catalytic properties of 1 and the most likely mechanism for CO2 reduction. The selectivity for CO2 over proton reduction is explained by analyzing the catalyst's affinity for the possible ligands present under typical reaction conditions: acetonitrile, water, CO2, and bicarbonate.

Framework vs. side-chain amphidynamic behaviour in oligo-(ethylene oxide) functionalised covalent-organic frameworks.

We present a family of covalent organic frameworks that have been functionalized with oligo-(ethylene oxide) chains of varying lengths. Because of the open structure of the COFs, the side chains do not interfere with their crystallization obtaining materials with predictable crystal structure. The difference in length of the side-chains allowed for the determination of amphidynamic behaviour with the use of 13C solid-state NMR relaxation methods.

General Theory of Absorption in Porous Materials: Restricted Multilayer Theory.

In this article, we present an approach for the generalization of adsorption of light gases in porous materials. This new theory goes beyond Langmuir and Brunauer-Emmett-Teller theories, which are the standard approaches that have a limited application to crystalline porous materials by their unphysical assumptions on the amount of possible adsorption layers. The derivation of a more general equation for any crystalline porous framework is presented, restricted multilayer theory.

Dirac cone in two dimensional bilayer graphene by intercalation with V, Nb, and Ta transition metals.

Bilayer graphene (BLG) is a semiconductor whose band gap and properties can be tuned by various methods such as doping or applying gate voltage. Here, we show how to tune electronic properties of BLG by intercalation of transition metal (TM) atoms between two monolayer graphene (MLG) using a novel dispersion-corrected first-principle density functional theory (DFT) approach. We intercalated V, Nb, and Ta atoms between two MLG.

Modulating Electrocatalysis on Graphene Heterostructures: Physically Impermeable Yet Electronically Transparent Electrodes.

The electronic properties and extreme thinness of graphene make it an attractive platform for exploring electrochemical interactions across dissimilar environments. Here, we report on the systematic tuning of the electrocatalytic activity toward the oxygen reduction reaction (ORR) via heterostructures formed by graphene modified with a metal underlayer and an adlayer consisting of a molecular catalyst. Systematic voltammetric testing and electrochemical imaging of patterned electrodes allowed us to confidently probe modifications on the ORR mechanisms and overpotential.

Low-temperature Synthesis of Heterostructures of Transition Metal Dichalcogenide Alloys (WMoS) and Graphene with Superior Catalytic Performance for Hydrogen Evolution.

Large-area (∼cm) films of vertical heterostructures formed by alternating graphene and transition-metal dichalcogenide (TMD) alloys are obtained by wet chemical routes followed by a thermal treatment at low temperature. In particular, we synthesized stacked graphene and WMoS alloy phases that were used as hydrogen evolution catalysts. We observed a Tafel slope of 38.

Design Principles for High H Storage Using Chelation of Abundant Transition Metals in Covalent Organic Frameworks for 0-700 bar at 298 K.

Physisorption is an effective route to meet hydrogen gas (H) storage and delivery requirements for transportation because it is fast and fully reversible under mild conditions. However, most current candidates have too small binding enthalpies to H which leads to volumetric capacity less than 10 g/L compared to that of the system target of 40 g/L at 298 K. Accurate quantum mechanical (QM) methods were used to determine the H binding enthalpy of 5 linkers which were chelated with 11 different transition metals (Tm), including abundant first-row Tm (Sc through Cu), totaling 60 molecular compounds with more than 4 configurations related to the different number of H that interact with the molecular compound.

Prediction of the crystal packing of di-tetrazine-tetroxide (DTTO) energetic material.

Previous calculations suggested that di-tetrazine-tetroxide (DTTO), aka tetrazino-tetrazine-tetraoxide, might have a particularly large density (2.3 g/cm(3) ) and high energy release (8.8 kJ/kg), but it has not yet been synthesized successfully.