Tuning 2D Magnetism in Cobalt Monoxide Nanosheets Via In Situ Nickel‐Doping

Abstract

Element doping has become an effective strategy to engineer the magnetic properties of two-dimensional (2D) materials and is widely explored in van der Waals layered transition metal dichalcogenides. However, the high-concentration substitution doping of 2D nonlayered metal oxides, which can preserve the original crystal texture and guarantee the homogeneity of doping distribution, is still a critical challenge due to the isotropic bonding of closed-packed structures. In this work, the synthesis of high-quality 2D nonlayered nickel-doped cobalt monoxide nanosheets via in situ atmospheric pressure chemical vapor deposition method is reported. High-resolution transmission electron microscopy confirmed that nickel atoms are doped at the intrinsic cobalt atom sites. The nickel doping concentration is stable at ≈15%, superior to most magnetic dopants doping in 2D materials and metal oxides. Magnetic measurements showed that pristine cobalt monoxide is nonferromagnetic, whereas nickel-doped cobalt monoxide exhibits robust ferromagnetic behavior with a Curie temperature of ≈180 K. Density functional theory calculations reveal that nickel atoms can improve the internal ferromagnetic correlation, giving rise to significant ferromagnetic performance of cobalt monoxide nanosheets. These results provide a valuable case for tuning the competing correlated states and magnetic ordering by substitution doping in 2D nonlayered oxide semiconductors.

Recent Advances of Emerging Metal-Containing Two-Dimensional Nanomaterials in Tumor Theranostics

“…[6][7][8][9][10][11][12][13][14][15][16] Among them, metal-containing 2D materials have become a research frontier in nano-medicine, benefiting from their strong near-infrared (NIR) light absorption, ultrasonic responsiveness and the capacity to produce reactive oxygen species (ROS). [17][18][19][20] Currently, there are mainly two types of metal-containing 2D materials, depending on whether metal species are decorated on the surface of 2D materials or take up the skeleton structures. Thanks to the performance modulation of metal species, which endows 2D materials with highly catalytic performance as well as light and sonic responsive ability, these materials are well suited for cancer PDT, PTT, CDT, SDT, and other types of therapy.…”

Controlled Growth and Size-Dependent Magnetic Domain States of 2D γ-Fe2O3

“…Cheng et al reported the synthesis of ultrathin cobalt ferrite nanoflakes, which exhibit a Curie temperature as high as 390 K . As these nonlayered 2D magnets possess magnetic order above room temperature and enhanced chemical stability in comparison to most existing van der Waals magnets, they offer remarkable opportunities for constructing practical magnetic heterostructure devices with potential applications. − Until now, the investigation of nonlayered magnetic nanoflakes is still in its infancy due to the inadequate means of controllable 2D growth and a limited understanding of the detailed magnetic properties.…”