Surface chemical-modification of inorganic two-dimensional nanomaterials for engineering the intrinsic magnetic properties and related applications

Recently, due to the novel spin structures and unique magnetic states, the magnetic properties of two-dimensional (2D) nanomaterials, especially monolayer or few-layer inorganic ultrathin nanosheets, exhibit great promise for the next-generation spintronics. As is known, practical application usually requires materials with magnetic properties which can be deliberately regulated by external control parameters, such as, applied electric fields, elastic stress or light. However, most of the 2D inorganic nanomaterials are intrinsically non-magnetic. To tackle this challenge, tremendous efforts have been dedicated to effectively tuning the magnetic properties of two-dimensional nanomaterials, such as, transitional metal atoms doping and point defects, which provide feasible ways of magnetic modulation to induce magnetism. Unfortunately, compared with the high demands of practical magnetic application, there is still way to inducing magnetism in two-dimensional nanomaterials in a precise and controlled manner. In this regard, how to effectively obtain magnetic two-nanomaterials remains a great but noteworthy challenge. Atomic-scale-thickness 2D nanomaterials possess extremely large specific surface area, making their surface phase as important as bulk counterparts. Compared to bulk counterparts, the ultrathin nanosheets with outmost atom layers exposed are more vulnerable to the surface modification, which has been theoretically and experimentally confirmed. Therefore, surface chemical modification of inorganic 2D nanomaterials offers a novel way to engineer intrinsic magnetic properties of 2D nanomaterials. Furthermore, the exposed high specific surface area and quantum confinement of electrons in the two-dimensional nanomaterials endow the surface chemical modification strategies to regulate the intrinsic magnetic properties in a controllable and precise manner. In this review, we focus on recent research about regulation strategies of magnetic behaviors, especially concerning surface chemical modification strategies, which bring about novel magnetic inorganic two-dimensional materials. For instance, introducing hydrogen dangling bonds into graphitic carbon nitride nanosheets successfully inducing ferromagnetism; surface adsorption of hydrazine molecules onto two-dimensional NbSe 2 nanosheets triggering the distortion of Nb-Se covalent bond, which results in the spin polarization; surface molecules meditating synthesis of ultrathin VSe 2 nanosheets which display ferromagnetism and charge density wave. Benefiting from regulated magnetic properties, inorganic two-dimensional nanomaterials deliver promising magnetic energy conversion and magnetic response applications, which ranges from the giant magnetoresistance, magnetocaloric effect to efficiently hydrogen evolution. Surface-chemical modification of two-dimensional nanomaterials has seen the advance for regulating their intrinsic magnetic properties.