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Half-metallic (HM) ferromagnets (HM-FMs) with large HM gap and high Curie temperature (TC) have a great importance in the field of spintronics. In this study, the geometric features, electronic structure and magnetism of two new double perovskites (DPs) represented by Rb2XMoO6 (X = Cr, Sc) were explored in bulk phase and (001) surface using quantum mechanical total energy calculations based on density functional theory (DFT). The results showed that optimized lattice constant a is 7.96 Å and 8.26 Å for Rb2CrMoO6 (RCMO) and Rb2ScMoO6 (RSMO), respectively, in the cubic phase (space group Fm-3m, #225). The cohesive energy Ecoh, formation energy Efor and elastic constants (mechanical) calculations proved that present materials are stable. The magnetic properties were explored in terms of ground state magnetic coupling, total magnetic moment (M) and atomic magnetic moment (m), exchange energy (J), and Curie temperature. It was found that both materials have ferromagnetic coupling in the ground state, with M of integer value of 8.0 μ B (4.0 μ B), J value of 47 meV(72 meV) and TC of 365 K (557 K) in Rb2CrMoO6 (Rb2ScMoO6). The electronic properties computed with electronic band structure and density of states demonstrated both DPs to be half-metal with HM gap of 1.61 eV (2.1 eV) in Rb2Cr-based (Rb2Sc-based) system. Finally the electronic and magnetic properties of (001) surfaces were investigated and compared with that of bulk phase. Interestingly, bulk HM property was retained in RSMO, but disappeared in RCMO due the emergence of defect states at Fermi level (EF). The reported results suggest that Rb-based DPs carry some fascinating properties for spin-based devices.

Single‐molecule junctions that are sensitive to compression or elongation are an emerging class of nanoelectromechanical systems (NEMS). Although the molecule–electrode interface can be engineered to impart such functionality, most studies to date rely on poorly defined interactions. We focused on this issue by synthesizing molecular wires designed to have chemically defined hemilabile contacts based on (methylthio)thiophene moieties. We measured their conductance as a function of junction size and observed conductance changes of up to two orders of magnitude as junctions were compressed and stretched. Localised interactions between weakly coordinating thienyl sulfurs and the electrodes are responsible for the observed effect and allow reversible monodentate⇄bidentate contact transitions as the junction is modulated in size. We observed an up to ≈100‐fold sensitivity boost of the (methylthio)thiophene‐terminated molecular wire compared with its non‐hemilabile (methylthio)benzene counterpart and demonstrate a previously unexplored application of hemilabile ligands to molecular electronics., Contact request: Molecular junctions with hemilabile contact moieties show enhanced mechanoresistive behaviour. The molecule–metal contact is forced to transition from a monodentate to a bidentate configuration as the junction is compressed and stretched, with a resulting modulation in conductance of up to two orders of magnitude.

High electrical conductance molecular nanowires are highly desirable components for future molecular-scale circuitry, but typically molecular wires act as tunnel barriers and their conductance decays exponentially with length. Here, we demonstrate that the conductance of fused-oligo-porphyrin nanowires can be either length independent or increase with length at room temperature. We show that this negative attenuation is an intrinsic property of fused-oligo-porphyrin nanowires, but its manifestation depends on the electrode material or anchor groups. This highly desirable, nonclassical behavior signals the quantum nature of transport through such wires. It arises because with increasing length the tendency for electrical conductance to decay is compensated by a decrease in their highest occupied molecular orbital-lowest unoccupied molecular orbital gap. Our study reveals the potential of these molecular wires as interconnects in future molecular-scale circuitry.

Electrocatalytic water splitting is a promising solution to resolve the global energy crisis. Tuning the morphology and particle size is a crucial aspect in designing a highly efficient nanomaterials-based electrocatalyst for water splitting. Herein, green synthesis of nickel oxide nanoparticles using phytochemicals from three different sources was employed to synthesize nickel oxide nanoparticles (NiOx NPs). Nickel (II) acetate tetrahydrate was reacted in presence of aloe vera leaves extract, papaya peel extract and dragon fruit peel extract, respectively, and the physicochemical properties of the biosynthesized NPs were compared to sodium hydroxide (NaOH)-mediated NiOx. Based on the average particle size calculation from Scherrer’s equation, using X-ray diffractograms and field-emission scanning electron microscope analysis revealed that all three biosynthesized NiOx NPs have smaller particle size than that synthesized using the base. Aloe-vera-mediated NiOx NPs exhibited the best electrocatalytic performance with an overpotential of 413 mV at 10 mA cm−2 and a Tafel slope of 95 mV dec−1. Electrochemical surface area (ECSA) measurement and electrochemical impedance spectroscopic analysis verified that the high surface area, efficient charge-transfer kinetics and higher conductivity of aloe-vera-mediated NiOx NPs contribute to its low overpotential values.

Together with the more intuitive and commonly recognized conductance mechanisms of charge‐hopping and tunneling, quantum interference (QI) phenomena have been identified as important factors affecting charge transport through molecules. Consequently, establishing simple, flexible molecular design strategies to understand, control and exploit QI in molecular junctions poses an exciting challenge. Here we demonstrate that destructive quantum interference (DQI) in meta‐substituted phenylene ethylene‐type oligomers (m‐OPE) can be tuned by changing the position and conformation of pendant methoxy (OMe) substituents around the central phenylene ring. These substituents play the role of molecular‐scale ‘taps’, which can be switched on or off to control the current flow through a molecule. Our experimental results conclusively verify recently postulated magic ratio and orbital product rules, and highlight a novel chemical design strategy for tuning and gating DQI features, to create single‐molecule devices with desirable electronic functions.

We use a scanning tunneling microscope to form and electrically interrogate metal - molecule - metal junctions. To form such junctions, molecules must be functionalised with suitable contact groups (e.g. thiols, thioethers, 4-pyridyls, amines) at each extremity. We show here that 2-(methylthio)thiophene units not only act as contact groups, but can reversibly switch between a monodentate configuration (MeS-only) and a bidentate configuration (MeS- and thienyl S) upon junction compression; as the junction is compressed the electrical conductance increases greatly with the increased molecule-contact interaction. This means that such molecules show a large-amplitude mechanical switching behavior; we also show that this is reversible and that switching can occur at a rate of at least 10 kHz. Control molecules with MeSC6H5 contact groups do not show this behavior. This, together with detailed theoretical and transport calculations on the compressed and extended molecular junctions, supports our contention that it is the thienyl S that is involved in the switching mechanism.