Given their unique properties, tremendous progress is realized in the use of nanostructured materials for various applications. However, their incorporation and fabrication into prototypic devices remain challenging due to their limited ability to form hierarchical 3D structures through the use of large scale, low cost, and facile processes. Herein, this challenge is addressed and the growth of unique hierarchical structures is demonstrated by coating calcareous foraminiferal shells with metal oxide materials via simple and inexpensive processes conducted on a large scale. Foraminifera are highly diverse and abundant marine unicellular protists surrounded by large, ranging from 0.1 mm to more than 200 mm in size, identical porous, and complex hierarchical shells. In the present study, these hierarchal structures are investigated in electrochemical water oxidation reactions and tested in terms of their ability to purify water from inorganic (metal ions) contaminates. The remarkable performances of the prototype filters and catalysts developed here, among the best recorded values in both fields, are reported. These findings thus open new perspectives for catalytic and water purification applications.

Controlled assembly of nanostructures is a key challenge in nanotechnology. In this work, we introduce an approach for the controlled assembly of 1D nanodumbbellsAu-tipped semiconductor nanorodsinto arbitrary 2D higher architectures, by their chemical docking to nanopatterned functionalities. We realized the docking functionalities via nanoimprinted metallic nanodots functionalized with an organic monolayer, whose terminal thiol groups chemically bind the nanodumbbell tips. We demonstrated that the functional nanopattern encodes the nanodumbbell assembly and can be designed to deterministically position nanodumbbells in two possible modes. In the single-docking mode, the nanodot arrays are designed with a spacing that exceeds the nanodumbbell length, restricting each nanodumbbell to dock with one edge and physically connect with its free edge to one of the neighboring nanodumbbells. Alternatively, in the double-docking mode, the nanodots are spaced to exactly fit the nanodumbbell length, allowing nanodumbbell docking with both edges. We found that the docking kinetics can be described by a random attachment model, and verified that for the used docking chemistry, nanodumbbells that are docked to the same dot do not interact with each other. Our work demonstrates the possibility for massively parallel positioning of sub-100 nm 1D semiconductor nanostructures, and can potentially enable their future integration into functional nanodevices and nanosystems.

Two-dimensional CdS-based hybrid nanostructures are intriguing materials with an application prospect in different fields such as sensing (i. e., photoresistors) and solar energy harvesting (photocatalysis, photovoltaics, and so forth). We report herein a colloidal synthetic path for interfacing metal and semiconductor with 2D CdS nanoplates. Selective growth of Au, Pt, and a PtNi alloy as well as Cu 2−x S semiconductor is achieved on CdS nanoplates using controlled reduction of metallic precursors and thermal decomposition of a metal-sulfide single-source precursor using standard organic-phase colloidal chemistry.

The novel ensuing functionalities of complex nanostructures are driving the surging interest in their conceptualization and realization. Despite the significant synthetic developments in multicomponent hybrid nanostructure (HNS) formation, development of selective chemistry to tune the properties of HNSs will always be one of the major demands in colloidal synthesis. Synthesis of complex HNSs with a predicted morphology is particularly challenging using traditional strategies as the seeded growth due to surface chemistry limits. In the present work, we investigate the role of a metal oxide (MO) domain on the insertion of a CdS nanorod via a solution–liquid–solid mechanism between heterodimers of Au–MO. By choosing different compositions and crystalline structures for the MOs (namely, Fe3O4 and MnO), we demonstrate and explore the mechanism that allows the MO to dictate the chemoselective growth of the CdS domain. Additionally, a kinetic study unravels the role of the crystalline structure at a CdS–Fe3O4 interface on the final HNS shape.

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.