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Adsorption, desorption, and diffusion dynamics of hydrogen gas molecules over a hexagonal ZnO monolayer have been studied thoroughly in the van der Waals Density Functional Theory (vdW-DFT) framework in association with kinetic Monte Carlo (kMC) simulations. Hydrogen molecules can attach to a ZnO sheet via a weak physisorption process with a limitation of maximum attachment of three molecules per hexagonal ring. Pressure and temperature are the main deciding parameters for the overall storage capacity of hydrogen on a ZnO substrate. kMC simulations are performed to capture the stochastic behavior of surface dynamics of gas molecules. Adsorption energy and diffusion barrier are predicted to be around 50–60 meV and 4–12 meV, respectively, according to vdW-DFT calculations. kMC simulations with these energy parameters estimate the surface coverage of hydrogen to be pretty high below room temperature and high pressure. Furthermore, the hydrogen adsorption in the ZnO monolayer leads to the increase of the bandgap value, subsequently changing the conductivity of the material. The present research work sheds light on the usage of a ZnO monolayer for suitable hydrogen gas storage and sensing applications. [ABSTRACT FROM AUTHOR]

Electronic and magnetic properties of transition metal (TM) ion-doped monolayer zinc oxide (ML-ZnO) have been analyzed using ab-initio calculations in the frame work of density functional theory. Spin–spin interaction study reveals that Cr, Mn, Fe and Cu doped at Zn site of ML-ZnO show stable ferromagnetic ordering along with the half-metallic behavior for most of the cases. The electronic and magnetic properties of the pristine system can also be modified by using co-doping. 3d orbital electrons of the dopants are primarily responsible for the origin of magnetic moment and the remaining part comes from the 3d and 2p orbital electrons of Zn and O atoms, respectively. Moreover, the magnetic ordering in Fe-doped ML-ZnO can change with the doping distance between the dopants. [ABSTRACT FROM AUTHOR]

A large surface area, wide band gap, and unique bonding property between Zn and O atoms make the hexagonal ZnO monolayer attractive as a gas sensor. In the present work, the adsorption and evolution of nitrogen (N2) molecules over a ZnO monolayer have been studied using two different theoretical methods: van der Waals density functional theory (vdW-DFT) and kinetic Monte-Carlo (kMC) simulation. The adsorption and diffusion (hopping over the surface) energy of a N2 gas molecule has been calculated considering the different sites over the ZnO substrate using the revPBE-vdW functional. Bader charge, electron localization function analysis, density of states and band structure plotting have been used to understand the adsorption mechanism. Lateral repulsive interaction between two N2 molecules limits the maximum packing number of gas molecules within one hexagonal ring. The output of the vdW-DFT calculation has been fed to the kMC code to predict the rate of adsorption, desorption, and diffusion, along with the overall surface coverage at different temperatures and pressures. Finally, the change in the N2 adsorption energy has been predicted with the increase of the ZnO layer number. [ABSTRACT FROM AUTHOR]

Magnetic properties of 3d transition metal ion doped methylammonium lead chloride (MAPbCl3) have been studied by ab-initio calculations in the framework of density functional theory. The study of spin–spin interactions reveals that doping (about 2%) of Ti, V, Cr, Mn and Fe at the Pb site of MAPbCl3 shows stable ferromagnetic ordering along with the half-metallic behaviour. 3d orbital electrons of the dopants are primarily responsible for the origin of the magnetic moment and the remaining part comes from the p-d exchange interaction between the 3d orbital electrons of the dopants and the 6p orbital electrons of Pb in the vicinity of the doping position. Additionally, the band structure calculations suggest that the doped system shows n/p-type semiconducting behaviour. Ferromagnetism, along with semiconducting behaviour in transition metal ion-doped MAPbCl3, will be suitable for spintronic applications. [ABSTRACT FROM AUTHOR]

A 2.45 GHz electron cyclotron resonance (ECR) ion source coupled to a gas-jet skimmer system has been developed for the online production of radioactive ion beams (RIBs). Using radial injection of gas jet in the ion source, RIBs of 11C1+, 11CO21+, and 11CO1+ have been produced online with beam intensity up to about 9 × 103 particles per second for a 1 µA primary proton beam bombarding a nitrogen gas target. The details of the gas jet coupled ECR ion source and the results for stable isotope beams and RIBs are reported. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the impressive electrocatalytic hydrogen evolution (HER) capabilities of a self-assembled p–n homojunction in SnS2 nanosheets enriched with sulfur vacancies (VS) and tin vacancies (VSn). Our experiments demonstrate that after aqueous washing, SnS2 nanosheets washed ten times (S10) contain more VS and VSn than those washed three times (S3). As a result, S10 exhibits a significantly better HER performance than S3, with an overpotential of 119 mV at 10 mA/cm2, a Tafel slope of 140 mV/dec, a turnover frequency of 10.9 m/s, and faster H+ mass transport. S10 exhibits improved HER performance with an overpotential of 116 mV at 10 mA/cm2 and a Tafel slope of 96 mV/dec in the visible spectrum due to VS and better interfacial carrier separation from the p–n homojunction. Our partial density of states and Gibbs free energy calculation for H adsorption (ΔGH) reveal that undercoordinated Sn atoms near VS contribute to H adsorption in both S3 and S10. However, as S10 contains more VS than S3, its HER activity is superior. Our findings suggest that defect engineering through a simple and effective chemical synthesis approach can optimize the electro- and photoelectrochemical HER activity of layered two-dimensional SnS2 nanosheets. [ABSTRACT FROM AUTHOR]

Dilute magnetic semiconductor (DMS) is a trending research topic in material science for its requirements in spintronics technology in recent times. The present work reports the electrical and magnetic properties of different transition metal ions (Ti, V, Cr, Mn, Fe, Co, Ni and Zn)- doped silver copper sulphide. The dilute doping of transition metal ions at the copper site induces significant magnetic moments, which ordered ferromagnetically. The 3d orbital of the transition metal ions and the d orbital of Cu and Ag ions are the source of magnetisation. [ABSTRACT FROM AUTHOR]

CoFe2-xBixO4 nanoferrites with x=0, 0.05, 0.1, 0.5, and 1.0 have been synthesized by the glycine nitrate process. The present study investigates the effect of Bi3+ substitution on the microstructural, dielectric, ferroelectric, magnetic, and Mossbauer properties of CoFe2O4 nanoparticles. The X-ray diffraction technique was used to confirm the phase purity and estimate the crystallite size which revealed the formation of a secondary phase when Bi3+ concentration exceeds x=0.5. Transmission electron microscopy indicated the formation of grains by aggregation of small crystallites with a reduction in grain size to 20nm with an increase in Bi3+ content and also divulged the lattice parameter value to be 8.378Å , confirming the crystalline nature of the synthesised sample. Dielectric properties performed in the frequency range of 100Hz to 1MHz determined that the dielectric behavior is attributed to the Maxwell-Wagner polarization and the activation energy of the specimens is calculated from the dielectric measurements. The hysteresis curve indicated the ferrimagnetic nature of the samples. The samples also exhibited a well saturated P-E loop with gradual lowering in remenant polarization, coercive field, and saturation polarization with an increase in bismuth concentration. Mössbauer spectroscopy analysis confirmed the changes in magnetic moment of ions, their coupling with neighbouring ions, and cation exchange interactions. Owing to the high physical, thermal, and chemical stabilities, these magnetic ceramics, CoFe2-xBixO4, possesses tremendous potential in major understanding of magnetism and in magnetic recording applications for high density information storage. [ABSTRACT FROM AUTHOR]