Alkaline earth atom doping-induced changes in the electronic and magnetic properties of graphene: a density functional theory study

First-Principles Calculations with Six Structures of Alkaline Earth Metal Cyanide A(CN)2 (A = Be, Mg, Ca, Sr, and Ba): Structural, Electrical, and Phonon Properties

This work examines six structures (P4̅3m, P4₂ nm, R3m, P2₁/c, R3̅m, and C2/m) of alkaline earth metal cyanide A(CN)₂ (A = Be, Mg, Ca, Sr, and Ba) using first-principles calculations. The symmetries of P4̅3m, P4₂ nm, and R3m reflect a variation of Pn3̅m, previously reported as occurring on Be(CN)₂ and Mg(CN)₂ in X-ray diffraction studies, while the symmetries of P2₁/c, R3̅m, and C2/m were selected from the P3̅m1 symmetry found using Mg(OH)₂ as the initial structures, with -OH being replaced by -CN. The band structure, density of states, and phonon properties of all A(CN)₂ structures were then investigated using density functional theory (DFT), with a generalized gradient approximation (GGA) applied for the exchange and correlation energy values. The simulation results for the phonon spectra indicate that the stable structures are Be(CN)₂ (P4̅3m, P4₂ nm, and C2/m), Mg(CN)₂ (P4̅3m, P4₂ nm, and C2/m), Ca(CN)₂ (P2₁/c), Sr(CN)₂ (P2₁/c and R3̅m), and Ba(CN)₂ (R3̅m) at 0 GPa. For the effects of high pressure, Ca(CN)₂ and Sr(CN)₂ were thus found to be stable as C2/m at pressures above 10 and 3 GPa, respectively, while Ca(CN)₂ is as stable as R3̅m above 15 GPa. In the calculated band structures, all of the compounds with the C2/m structure demonstrated good conductivity, while the other structures have a band gap range of 2.83-6.33 eV.

Engineering at Subatomic Scale: Achieving Selective Catalytic Pathways via Tuning of the Oxidation States in Functionalized Single-Atom Quantum Catalysts

Regulating the catalytic pathways of single-atom sites in single atom catalysts (SACs) is an exciting debate at the moment, which has redirected the research towards understanding and modifying the single-atom catalytic sites through various strategies including altering the coordination environment of single atom for desirable outcomes as well as increasing their number. One useful aspect concerning the tunability of the catalytic pathways of SACs, which has been overlooked, is the oxidation state dynamics of the single atoms. In this study, iron single-atoms (FeSA) with variable oxidation states, dependent on the precursors, are harnessed inside a nitrogen-rich functionalized carbon quantum dots (CQDs) matrix via a facile one-step and low-temperature synthesis process. Dynamic electronic properties are imparted to the FeSAs by the simpler carbon dots matrix of CQDs in order to achieve the desired catalytic pathways of reactive oxygen species (ROS) generation in different environments, which are explored experimentally and theoretically for an in-depth understanding of the redox chemistry that drives the alternative catalytic pathways in FeSA@CQDs. These alternative and oxidation state-dependent catalytic pathways are employed for specific as well as cascade-like activities simulating natural enzymes as well as biomarkers for the detection of cancerous cells.

Effect of the number of nitrogen dopants on the electronic and magnetic properties of graphitic and pyridinic N-doped graphene - a density-functional study

Doping with nitrogen atom is an effective way to modify the electronic and magnetic properties of graphene. In this paper, we studied the effect of the number of dopant atoms on the electronic and magnetic properties of the two most common nitrogen bond configurations in N-doped graphene, that is, graphitic and pyridinic, using density functional theory (DFT). We found that the formation of graphitic and pyridinic configurations can initiate the transition of the electronic properties of graphene from semimetal to metal with n-type conductivity for the graphitic configuration and p-type conductivity for the pyridinic configuration. The formation of a bandgap-like structure was observed in both configurations. The bandgap increased with the increase in the number of dopant atoms. We also observed that the formation of graphitic configuration did not cause a transition to the magnetic properties of graphene even though the number of dopant atoms was increased. In the pyridinic configuration, the increase in the number of dopant atoms caused graphene to be paramagnetic, with the remarkable total magnetic moment of 0.400 μ_B per cell in the pyridinic-N₃ model. This study provides a deeper understanding of the modification of electronic and magnetic properties of N-doped graphene by controlling the bond configuration and the number of nitrogen dopants.

The number of dopant atoms is a parameter that can effectively tune the electronic and magnetic properties of graphitic and pyridinic N-doped graphene.