Calcareous Foraminiferal Shells as a Template for the Formation of Hierarchal Structures of Inorganic Nanomaterials

Abstract

A microorganism template approach has been explored for the fabrication of various well-defined three-dimensional (3D) structures. However, most of these templates suffer from small size (few μm), difficulty to remove the template, or low surface area, which affect their potential use in different applications or makes industrial scale-up difficult. Conversely, foraminifer’s microorganisms are large (up to 200 mm), consist of CaCO3 (easy to dissolve in mild acid), and have a relatively high surface area (≈5 m2 g–1). Herein, we demonstrate the formation of hierarchical structures of inorganic materials using calcareous foraminiferal shells such as Sorites, Globigerinella siphonifera, Lox-ostomina amygdaleformis, Calcarina baculatus or hispida, and Peneroplis planatus. Several techniques, such as thermal decomposition of single-source precursors of metal oxides or sulfides, reduction of metal salts directly on the surfaces, and redox reactions, were used for coating of different shell materials and several hybrid compositions, which possess nanofeatures. Finally, we examined the role of the prepared 3D structures on the reduction of 4-nitrophenol (4-NP), ethanol electrooxidation, and water purification. A remarkable performance was achieved in each application. The hierarchical structure leads to the reduction of 4-NP within several minutes, a 27 mA cm–2 current density peak was obtained for ethanol electrooxidation, and more than 95% of the organic dye contaminants were successfully removed. These results show that using foraminiferal shells offers a new way for designing complex hierarchical structures with unique properties.

Formation of Copper Oxide Nanotextures on Porous Calcium Carbonate Templates for Water Treatment

“…We demonstrate the activity of the proposed system in this work by removing heavy metal cations (Pb 2+ and Cd 2+ ) from water and in the degradation of methylene blue (MB). In our previous work, we have shown the contribution of the porous 3D structure ( Sorites -based) relative to their 2D counterparts [ 36 ]. Based on these results, we have chosen to deposit the active copper oxides on the porous structures.…”

“…In addition to the net-like structure, the Sorites has internal tunnels that connect its holes. We believe that these tunnels may confine the reactants, which increases the collision probability of the reactant molecules, and in turn, improves the performance of the active material [ 34 , 35 , 36 ].…”

Preparation of Hybrid Sol-Gel Materials Based on Living Cells of Microorganisms and Their Application in Nanotechnology

“…Such advantages as a rich variety of shapes, low cost and availability, ecological compatibility, unique configuration, and high repeatability of morphology ensure a high demand for microorganisms as templates in the molecular imprinting process. However, the difficulty of removing microorganisms and their small surface area is a limiting factor for their use in various applications and hinders scaling [ 119 ].…”

Metal/semiconductor interfaces in nanoscale objects: synthesis, emerging properties and applications of hybrid nanostructures

“… 300 As a model electrocatalytic system, our group demonstrated EtOH oxidation using an insulating 3D scaffold of CaCO 3 from a marine origin ( Sorites ), coated with cobalt and gold. 301 …”