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The sluggish kinetics of the oxygen reduction reaction (ORR) is the major hurdle for the development of efficient fuel cells. Since the conventional Pt based catalysts are very expensive, development of noble metal free catalysts for accelerating the kinetics of oxygen reduction reactions is highly important. Here, we explored transition metal (Fe, Co, Ni and Cu) decorated over the nitrogen and phosphorous co-doped graphene as single atoms catalyst. Among the four metal decorated systems considered, oxygen molecule is found to bind with only Fe and Co systems. Both the Fe and Co decorated systems were systematically investigated for their activity towards the oxygen reduction reaction through the four-electron reduction path. From the free energies calculated for all the intermediate reactions of ORR, Fe-decorated system was found to have lower overpotential as compared to the Co-decorated system indicating the former one as superior catalyst for ORR.

It is well known that a nuclear reactor generates various fission products including radioactive fission gases made of isotopes of Xe and Kr. The separation of Xe and Kr isotopes and their entrapme...

Invited for the cover of this issue are Sourav Pal, Gopalan Rajaraman and co-workers at the Indian Institute of Technology Bombay, the Bhabha Atomic Research Centre and the Indian Institute of Science Education and Research. The image depicts how a mixture of atmospheric gases such as CO

A new recyclable g-C3N4@PDMS heterogeneous catalyst has been developed as an efficient catalyst with an appreciable reactivity toward Knoevenagel condensation in the presence of crown ether (PTC). ...

Entrapment of radioactive inert gases, Xe and Kr, generated from the spent nuclear fuel reprocessing or nuclear accidents is one of the challenging issues in successful implementation of nuclear en...

By computing and analyzing the magnetic exchange coupling, binding energies, the partial density of states (pDOS), and adsorption isotherms for the pristine and gas bound MOFs [(Cr4(X)4Cl)3(BTT)8]3- (X=O2, N2, and H2), we unequivocally establish the role of spin-states and spin-coupling in controlling the gas selectivity. The computed geometries and gas adsorption isotherms are consistent with the earlier experiments. The O2 binding to the MOF follows an electron-transfer mechanism resulting in a Cr(III) superoxo species (O2-•) with a very strong antiferromagnetic coupling between the two centers, while N2/H2 found to only weakly perturb the metal center. Although the gas bound and unbound MOFs have S =0 ground state (GS), the nature of spin configurations and the associated magnetic exchanges are dramatically different. This study offers a hitherto unknown strategy of utilizing spin-state/spin-couplings to control gas adsorption selectivity in MOFs.

Computational high-throughput screening using molecular simulations is a powerful tool for identifying top-performing metal-organic frameworks (MOFs) for gas storage and separation applications. Accurate partial atomic charges are often required to model the electrostatic interactions between the MOF and the adsorbate, especially when the adsorption involves molecules with dipole or quadrupole moments such as water and CO2. Although ab initio methods can be used to calculate accurate partial atomic charges, these methods are impractical for screening large material databases because of the high computational cost. We developed a random forest machine learning model to predict the partial atomic charges in MOFs using a small yet meaningful set of features that represent both the elemental properties and the local environment of each atom. The model was trained and tested on a collection of about 320 000 density-derived electrostatic and chemical (DDEC) atomic charges calculated on a subset of the Computation-Ready Experimental Metal-Organic Framework (CoRE MOF-2019) database and separately on charge model 5 (CM5) charges. The model predicts accurate atomic charges for MOFs at a fraction of the computational cost of periodic density functional theory (DFT) and is found to be transferable to other porous molecular crystals and zeolites. A strong correlation is observed between the partial atomic charge and the average electronegativity difference between the central atom and its bonded neighbors.

An unprecedented air-stable, n-doped graphene field-effect transistor (GFET) with exceptionally enhanced mobility (500%), and concomitantly increased current density (∼105 A cm−2), using lanthanide macrocyclic complexes [Ln(L1)(NO3)3] (where Ln = La (1) or Ce (2)) is demonstrated. Such n-doped GFETs (n-GFETs) exhibit ambient stability for up to 7200 h, attributed to the inherent robustness of 1 and 2. Achieving stable and symmetric n-GFETs is mutually exclusive and elusive, underlining the significance of both high stability and symmetric electron- and hole-currents illustrated here. Interestingly, the influence of C–H⋯π interaction for the non-covalent charge-transfer between the dopant and GFET is established experimentally for the first time and strongly corroborated through computational investigations. Besides stabilizing n-doped GFETs, the C–H⋯π interaction unravels a previously unknown direction for electronic tuning of graphene. Importantly, spatial selectivity is achieved through sub-monolayer coverage (0.5–3.0 molecules per μm2) of the dopants using the femtojet dispensing route. This approach is synergistically combined with the air-stability of n-GFETs to realise complementary, bottom-gated logic inverters exhibiting the highest gain of 0.275 (at 2 V) and lowest power dissipation (∼30 μW), to realise next-generation molecular electronic devices.

Two-dimensional materials formed from the molecular self assembly of monomers through noncovalent interactions are of great importance in designing complex nanostructures with desired properties. The carbon nitride based heterocyclic systems, triazine and heptazine, are found to be promising candidates for generating various self assembled materials through (N....H) hydrogen bonding. Here, we explored graphyne and graphdiyne-like self assembled structures for carbon nitride materials using the density functional theory calculations. We systematically investigated the monolayer structures, stacked structures in different configurations, as well as the surface assembled structures on the Au(111) surface. In all four different monolayer structures, the monomers interact through the N...H hydrogen bonding. The electronic structure results indicate that the electronic properties in these structures can be tuned through the variation in the length of the acetylinic unit. The minimum energy stacked bilayer structure of triazine based material exactly matches with the experimentally reported structure. Surface assembled studies of the triazine based system show strong interaction between the Au(111) surface and the carbon nitride monolayer. Graphical abstract Self assembled two-dimensional molecular materials as well as the surface assemblies of triazine and heptazine based precursors are computationally investigated.

Eu3+ and Dy3+ doped YP04 nanoparticles dispersible in methanol/water were prepared by the reaction of Y3+ and Eu3+/Dy3+ ions with ammonium dihydrogen phosphate in ethylene glycol medium at 160 °C. Nature and extent of strain associated with lattice has been found to change with incorporation of Eu3+/Dy3+ ion in the nanoparticles as well as the heat treatment temperature. Based on the TEM studies, it has been established that particles are highly crystalline with an average particle size of around 5 nm. Co-doping YP04:Eu nanoparticles with Dy3+ ions followed by annealing them at high temperature (900 °C) lead to reduction in both Eu3+ and Dy3+ luminescence intensities from the sample and this has been attributed to the clustering effect of the lanthanide ions. Refereed/Peer-reviewed