Templated Synthesis of Porous Capsules with a Controllable Surface Morphology and their Application as Gas Sensors

Abstract

Porous capsules composed of hematite, silica, and hematite–silica composites are prepared by a templated synthesis method. Polyelectrolyte multilayer‐coated particles (PEMPs) are used to synthesize goethite nanocrystals and the resulting goethite‐nanocrystal‐embedded PEMPs (PEMP–goethite) are then used as templates to form porous capsules. The surface morphology and surface area of the porous capsules can be controlled by the size of the PEMP–goethite template, which is determined by the extent of growth of the goethite nanocrystals. By controlling the surface morphology and area, it is also possible to tune the sensitivity of the hematite capsules for use as gas‐sensing materials. This surfactant‐free approach is also used to synthesize silica and silica‐based composite capsules with a controllable porous shell thickness. This straightforward approach can also be extended to the synthesis of other porous capsules or particles with a controllable surface morphology.

Hollow Micro‐/Nanostructures: Synthesis and Applications

“…Under this condition, uniform coating of templates can only be achieved by other interactions, for example, electrostatic attraction between the formed particles and the templates, [55] or the metal cations are exclusively entrapped chemically or physically near the template surface. [56] With the latter approach, Choi et al…”

“…[56] The Fe 2þ ions are first adsorbed into the polymer multilayers coated on melamineformaldehyde (MF) templates through LBL assembly. After several cycles of washing, the adsorbed ions are precipitated within the multilayers by treating with NaOH solution to form goethite.…”

Template‐free Formation of Uniform Urchin‐like α‐FeOOH Hollow Spheres with Superior Capability for Water Treatment

“…[21,24] Inspired by these ideas, we have investigated the application of sample A, with the highest surface area and largest total pore volume, in water treatment. Congo red, a dye commonly used in the textile industry, is chosen as a model organic water pollutant.…”

“…As a result, continuous efforts are being made on the preparation of complex 3D iron oxide nanostructures assembled from low-dimensional building blocks. [21,[23][24][25][26][27][28][29][30][31][32] Among them, 3D hollow structures with permeable shells and high surface area have emerged as an attractive material platform for water treatment. [15,[33][34][35][36][37][38][39] Hydroxy iron oxides (α-FeOOH, β-FeOOH) are usually used as precursors in preparing nanostructured Fe 2 O 3 .…”

Urchin-like FeOOH hollow microspheres decorated with MnO2 for enhanced supercapacitor performance

“…Iron oxides/hydroxides including Fe 2 O 3 , Fe 3 O 4 , and FeOOH exhibit great promise as anode materials [20][21][22][23][24][25], owing to their high theoretical capacitance, low cost, and environmental benignity. However, relatively low electrical conductivity and stability limit their capacitances at high current densities.…”