Tunable ferromagnetic ordering in phosphorus adsorbed ReS2 nanosheets.

Layered transition metal dichalcogenides (TMDs) are considered as promising materials for electronic, optoelectronic and spintronic devices due to their outstanding properties. Herein, based on rhenium disulfide (ReS2) nanosheets, we realized the intrinsic room temperature ferromagnetism with the adsorption of P adatoms (P-ReS2). Experiments indicate that the saturation magnetization (Ms ) can be tuned by the P ratios, where the maximum Ms can reach up to 0.0174 emu g-1. Besides, density functional theory (DFT) calculation results demonstrate that the strong hybridization between Re d and P p orbitals is the main reason of inducing ferromagnetism in P-ReS2 system. This work provides a novel method to engineer the magnetism of TMDs, endowing them with the possibility of spintronic applications.

Cr cation-anchored carbon nanosheets: synthesis, paramagnetism and ferromagnetism.

Since the successfully synthesis of monolayer graphene, carbon-based materials have attracted wide and extensive attentions from researches. Due to the excellent transport capacity and conductivity, they are promising to be applied in electronic devices, even substituting the silicon-based electronic devices, optoelectronics and spintronics. Nevertheless, due to the non magnetic feature, many efforts have been devoted to endow carbon materials magnetism to apply them in the spintronic devices fabrication. Herein, a strategy of Cr cation solely anchored on two-dimensional carbon nanosheets by Cr-N bonds is developed, which introduces magnetism in carbon nanosheets. By extended x-ray absorption fine structure characterization, Cr cations are demonstrated to be atomically dispersed with Cr-N3coordination. And after Cr-N3anchored, carbon nanosheets exhibit ferromagnetic features with paramagnetic background. The magnetization varies with Cr content and reaches the maximum (Cr: 2.0%, 0.86 emu g-1) under 3 T at 50 K. The x-ray magnetic circular dichroism and first-principle calculations indicate that the magnetism is caused by the Cr3+component of the anchored Cr cations. This study sets a single cation anchoring carbon as a suitable candidate for future spintronics.

Robust ferromagnetism in Cr-doped ReS2 nanosheets demonstrated by experiments and density functional theory calculations.

As one of the transition metal dichalcogenides (TMDs), ReS2 displays several outstanding properties, while the intrinsically nonmagnetic property limits its applications in spin-related devices. In this study, we selected Cr as the dopant to realize the robust room-temperature ferromagnetism in Cr-doped ReS2 (Cr-ReS2) nanosheets. The saturation magnetization (M s ) of the samples can be tuned by changing the Cr concentration. Density functional theory calculation results reveal that Cr dopant can provide the magnetic moments and stable ferromagnetic coupling in Cr-doped ReS2 system. This finding provides an effective approach for designing the new magnetic TMDs in spintronics devices.

Dual-Native Vacancy Activated Basal Plane and Conductivity of MoSe2 with High-Efficiency Hydrogen Evolution Reaction.

Although transition metal dichalcogenide MoSe2 is recognized as one of the low-cost and efficient electrocatalysts for the hydrogen evolution reaction (HER), its thermodynamically stable basal plane and semiconducting property still hamper the electrocatalytic activity. Here, it is demonstrated that the basal plane and edges of 2H-MoSe2 toward HER can be activated by introducing dual-native vacancy. The first-principle calculations indicate that both the Se and Mo vacancies together activate the electrocatalytic sites in the basal plane and edges of MoSe2 with the optimal hydrogen adsorption free energy (ΔGH* ) of 0 eV. Experimentally, 2D MoSe2 nanosheet arrays with a large amount of dual-native vacancies are fabricated as a catalytic working electrode, which possesses an overpotential of 126 mV at a current density of 100 mV cm-2 , a Tafel slope of 38 mV dec-1 , and an excellent long-term durability. The findings pave a rational pathway to trigger the activity of inert MoSe2 toward HER and also can be extended to other layered dichalcogenide.

Zigzag-edge related ferromagnetism in MoSe2 nanoflakes.

Outstanding magnetic properties are highly desired for two-dimensional ultrathin semiconductor nanosheets for their potential applications in nano-electronics and spintronics. Here, ultrathin MoSe2 nanoflakes with plenty of edges were prepared via an efficient chemical vapor deposition method. The magnetic measurement results indicate that the sample exhibits strong ferromagnetic behaviour with a saturation magnetization of 1.4 emu g(-1) at room temperature, where the ferromagnetism persists up to 700 K, revealing the high Curie temperature of this material. Density functional theory spin-polarized calculations predict that strong ferromagnetic moments in MoSe2 nanoflakes are attributed to the zigzag edges. Our findings also suggest that the MoSe2 nanoflakes with a high density of edge spins could be used to fabricate spintronic devices, which are circuits utilizing the spin of the electron to process and store information.

Ferromagnetism of two-dimensional transition metal chalcogenides: both theoretical and experimental investigations.

In recent years, with the fast development of integrated circuit electronic devices and technologies, it has become urgent to improve the density of data storage and lower the energy losses of devices. Under these circumstances, two-dimensional (2D) materials, which have a smaller size and lower energy loss compared with bulk materials, are becoming ideal candidates for future spintronic devices. Among them, 2D transition metal chalcogenides (TMCs), which have excellent electronic and optical properties, have attracted great attention from researchers. However, most of them are intrinsically non-magnetic, which severely hinders their further applications in spintronics. Therefore, introducing intrinsic room-temperature ferromagnetism into 2D TMC materials has become an important issue in spintronics. In this work, we review the introduction of intrinsic ferromagnetism into typical 2D TMCs using various strategies, such as defect engineering, doping with transition metal elements, and phase transfer. Additionally, we found that their ferromagnetism could be adjusted via changing the experimental conditions, such as the nucleation temperature, ion irradiation dose, doping amount, and phase ratio. Finally, we provide some insight into prospective solutions for introducing ferromagnetism into 2D TMCs, hoping to shed some light on future spintronics development.

Optimized Conductivity and Spin States in N-Doped LaCoO3 for Oxygen Electrocatalysis.

The spin state of antibonding orbital (eg) occupancy in LaCoO3 is recognized as a descriptor for its oxygen electrocatalysis. However, the Co(III) cation in typical LaCoO3 (LCO) favors low spin state, which is mediocre for absorbing oxygen-containing groups involved in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), thus hindering its further development in electrocatalysis. Herein, both experimental and theoretical results reveal the enhancement of bifunctional electrocatalytic activity in LaCoO3 by N doping. More specifically, electron energy loss spectroscopy and superconducting quantum interference devices magnetic analysis demonstrate that the Co(III) cation in N-doped LaCoO3 (LCON) achieves a moderate eg occupancy (≈1) compared with its low spin state in LaCO3. First-principle calculation results reveal that N dopants play a bifunctional role of tuning the spin-state transition of Co(III) cations and increasing the electrical conductivity of LCO. Thus, the optimized LCON exhibits an OER overpotential of 1.69 V at the current density of 50 mA/cm2 (1.94 V for pristine LCO) and yields an ORR limiting current density of 5.78 mA/cm2 (4.01 mA/cm2 for pristine LCO), which offers a new strategy to simultaneously modulate the magnetic and electronic structures of LCO to further enhance its electrocatalytic activity.

Bifunctional Oxygen Electrocatalyst of Mesoporous Ni/NiO Nanosheets for Flexible Rechargeable Zn-Air Batteries.

One approach to accelerate the stagnant kinetics of both the oxygen reduction and evolution reactions (ORR/OER) is to develop a rationally designed multiphase nanocomposite, where the functions arising from each of the constituent phases, their interfaces, and the overall structure are properly controlled. Herein, we successfully synthesized an oxygen electrocatalyst consisting of Ni nanoparticles purposely interpenetrated into mesoporous NiO nanosheets (porous Ni/NiO). Benefiting from the contributions of the Ni and NiO phases, the well-established pore channels for charge transport at the interface between the phases, and the enhanced conductivity due to oxygen-deficiency at the pore edges, the porous Ni/NiO nanosheets show a potential of 1.49 V (10 mA cm-2) for the OER and a half-wave potential of 0.76 V for the ORR, outperforming their noble metal counterparts. More significantly, a Zn-air battery employing the porous Ni/NiO nanosheets exhibits an initial charging-discharging voltage gap of 0.83 V (2 mA cm-2), specific capacity of 853 mAh g Zn -1 at 20 mA cm-2, and long-time cycling stability (120 h). In addition, the porous Ni/NiO-based solid-like Zn-air battery shows excellent electrochemical performance and flexibility, illustrating its great potential as a next-generation rechargeable power source for flexible electronics.

Structural distortion induced ferromagnetism in two-dimensional metal-free graphitic-C3N4 nanosheets.

With the assistance of innovative approaches driven by nanotechnology, engineering 2D materials into designed architectures or desired structures could tailor the electronic structure into an appropriate energy band structure, tuning the properties of the materials to be a predictable manner. Here we systematically studied the role that the structural distortion plays in the magnetism by taking two-dimensional metal-free graphitic-C3N4 as an example. Through the controllable structural distortion engineering introduced by post-heat-treatment in the experiment, the ferromagnetism is observed in graphitic-C3N4 nanosheets, which benefits from the electronic structural deformation, showing intriguing structural distortion-dependent ferromagnetism. This study not only offers new insight into the in-depth understanding of the structural distortion effect on the magnetism, but also provides a new way for searching and designing new magnetic materials.

Phase-transfer induced room temperature ferromagnetic behavior in 1T@2H-MoSe2 nanosheets.

Manipulating electronic and magnetic properties of two-dimensional transitional-metal dichalcogenides has raised a lot of attention recently. Herein we report the synthesis and ferromagnetic properties of phase-transfer induced room temperature ferromagnetic behavior in 1 T@2H-MoSe2 nanosheets. Experimental results indicate the saturated magnetization of the 1 T@2H-MoSe2 compound increases first and then decreases as the increasing of 1 T-MoSe2 phase, where 65.58% 1 T-MoSe2 phase incorporation in 2H-MoSe2 could enhance the saturated magnetization from 0.32 memu/g to 8.36 memu/g. Besides, obvious magnetoresistance behaviors are observed in these samples, revealing their potential applications in future spintronics.

Tunable ferromagnetic ordering in MoS2 nanosheets with fluorine adsorption.

Two-dimensional ferromagnetic ultrathin nanosheets hold great promise for next generation electronics and spintronics. Here, intrinsic ferromagnetism was achieved through a new effective strategy by fluorine adsorption on MoS2 nanosheets, where the fluorinated MoS2 nanosheets exhibit stable ferromagnetic hysteresis at room temperature with saturation magnetization of 0.06 emu g(-1) and magnetoresistance of 4.1%. The observed ferromagnetism can be tuned by changing the concentration of the adatom. On the basis of first-principle calculations, it is shown that not only fluorine absorbed MoS2 monolayer favours spontaneous spin polarization and local moment formation, but also that the spin moments can exhibit long range magnetic ordering. This work paves a new pathway to engineer the magnetic properties of the two-dimensional nano-materials.

Abnormal room temperature ferromagnetism in CuO-ZnO heterostructures: interface related or not?

We report the new functionality of room temperature ferromagnetism in CuO-ZnO heterostructures. Magnetic measurement results indicate the CuO-ZnO heterostructures show enhanced ferromagnetism contrary to the pure CuO (ZnO) and the observed ferromagnetism is proportional to the interface counts for the film-heterostructures, providing proof of interface related ferromagnetism. Our study suggests that magnetically functional interfaces could be an entirely new and novel design of magnetic materials for emergent devices.