Interface-Assisted Synthesis of the Mn_3–xFe_xO₄ Gradient Film with Multifunctional Properties

Abstract

Anisotropic gradient materials are considered as promising and novel in that they have numerous functional properties and are able to transform into hierarchical microstructures. We report a facile method of gradient inorganic thin film synthesis through diffusion-controlled deposition at the gas–solution interface. To investigate the reaction of interfacial phase boundary controllable hydrolysis by gaseous ammonium, an aqueous solution of FeCl3 and MnCl2 was chosen, as the precipitation pH values for the hydroxides of these metals differ gradually. As a result of synthesis using the gas–solution interface technique (GSIT), a thin film is formed on the surface of the solution that consists of Mn2+(Fe,Mn)2 3+O4 nanoparticles with hausmannite crystal structure. The ratio between iron and manganese in the film can be adjusted over a wide range by varying the synthetic procedure. Specific conditions are determined that allow the formation of a Mn–Fe mixed oxide film with a gradient of composition, morphology, and properties, as well as its further transformation into microscrolls with a diameter of 10–20 μm and a length of up to 300 μm, showing weak superparamagnetic properties. The technique reported provides a new interfacial route for the development of functional gradient materials with tubular morphology.

The ''rolling up'' effect of platinum layer obtained on nickel surface by interaction with solution of H2PtCl6 and its electrocatalytic properties in hydrogen evolution reaction during water electrolysis in alkaline medium

“…For example, novel metamaterials were obtained using this approach [1] and new types of 3D devices with small form factors [2][3][4]. There are also known works devoted to the synthesis and research of nanoscrolls of hydrosilicates of metals [5][6][7][8], as well as microtube of a number of oxides [9,10], fluorides [11] and sulfides of metals [12]. As shown by the authors of these works, the reason for this rolling up is mechanical forces that arise inside planar structures due to density or composition gradients.…”

Synthesis of the FeOOH Microtubes with Inner Surface Modified by Ag Nanoparticles

“…Moreover, the microtubes can be used as self-propelled motors, which are capable of converting chemical energy into driving forces for autonomous movement . Micro- and nanotubular structures with a scroll morphology can be obtained from two-dimensional (2D) materials by organic solvent-assisted lyophilization, hydrothermal synthesis, , and self-rolling of a strained bilayer of an inorganic semiconductor, , metallic, or polymer films, as well as rolling-up of interfacial gradient layer . The functionality of such structures is determined in large measures by the composition, structure, and physicochemical properties of the inner and outer surfaces of the tube walls.…”

“…9 Micro-and nanotubular structures with a scroll morphology can be obtained from two-dimensional (2D) materials by organic solvent-assisted lyophilization, 10 hydrothermal synthesis, 11,12 and self-rolling of a strained bilayer of an inorganic semiconductor, 13,14 metallic, 15 or polymer films, 16 as well as rolling-up of interfacial gradient layer. 17 The functionality of such structures is determined in large measures by the composition, structure, and physicochemical properties of the inner and outer surfaces of the tube walls. For example, in ref 18, the Ag NPs were synthesized on the surface of the microtube template to obtain a conductive coating.…”