Densification via bridging layers MXenes are a family of layered two-dimensional metal carbides and nitrides with interesting properties that can be lost if voids are formed during synthesis. By using a sequential combination of hydrogen and covalent bonding agents, Wan et al . were able to densify the layered structure and remove voids. This procedure leads to improvements in the mechanical strength and toughness, electrical conductivity, and shielding from electromagnetic interference. —MSL

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The ultimate frontier in nanomaterials engineering is to realize their composition control with atomic scale precision to enable fabrication of nanoparticles with desirable size, shape and surface properties. Such control becomes even more useful when growing hybrid nanocrystals designed to integrate multiple functionalities. Here we report achieving such degree of control in a family of rare-earth-doped nanomaterials. We experimentally verify the co-existence and different roles of oleate anions (OA−) and molecules (OAH) in the crystal formation. We identify that the control over the ratio of OA− to OAH can be used to directionally inhibit, promote or etch the crystallographic facets of the nanoparticles. This control enables selective grafting of shells with complex morphologies grown over nanocrystal cores, thus allowing the fabrication of a diverse library of monodisperse sub-50 nm nanoparticles. With such programmable additive and subtractive engineering a variety of three-dimensional shapes can be implemented using a bottom–up scalable approach.

A two-dimensional metal-organic framework (MOF) comprising nickel species and an organic ligand of benzenedicarboxylic acid is fabricated and explored as an electrocatalyst for urea oxidation reaction (UOR). The excellent UOR performance is found to be partially due to the high active site density of the two-dimensional MOF, and largely because of the high oxidation state of the nickel species.