Strategy for the Synthesis of Open Vase-Like Microcapsules Ordered Arrays with Transition Metal Oxyhydroxides Walls and Their Possible Practical Application

The review outlines the basic principles of a chemical strategy for obtaining arrays of open vase-like microcapsules (VLMs) with walls of metal oxyhydroxides on the surface of substrates. This strategy includes the steps of obtaining an array of similar microcapsules on the surface of an aqueous alkali solution by spraying a metal salt solution, removing excess reagents by washing with water, and transferring the resulting array to a substrate. The conditions for the formation of such microcapsules and their arrays at various stages of the process are analyzed and the conditions for obtaining VLM arrays with walls of NixFeOH, Mn3O4,Cu(OH)2/CuO, CeO2, and CeO2:Eux nanocrystals are considered. The unique morphology of such open microcapsules is noted, as a rule, to possess a special rim around the hole serving as a kind of “foundation” when they are fixed at the stage of transfer to the substrate surface. Attention is drawn to the possibility of using this approach to create VLMs with walls from a wide range of difficult-to-dissolve complex metal oxyhydroxides and their possible practical application as photonic materials, photothermal catalysts with the properties of “nano-greenhouses”, various kinds of electrode materials for electrochemical energy and sensors, microreactors and micromotors, etc. and prospects for further development of this methodology are outlined.