MESA+ University of Twente
Inorganic Materials Science Group


Towards self-assembled inorganic mesostructures

The increasing demands in emerging technologies are a driving force for materials scientists to develop new materials with advanced functionalities. If nano-sized objects are organized into mesoscale assemblies, such new materials can be envisioned. Within the CW-TOP program, the aim of this project is to develop strategies that combine synthesis and (self) assembly of nano-sized particles to form mesoscale materials. The resulting property will not directly be related to the properties of the building blocks, but will be determined by the multiple length scales in the assembly.

In the first phase of the project, the efforts will be focused on the development of new methodologies, as well as the use of well-established technologies from our laboratory, to synthesize new types of functional metal oxide nano-objects with full control over the size and shape of the object.

In a first route, nanosheets will be utilized as seed layer for epitaxial growth of metal oxide materials. The ability to grow epitaxial layers on nanosheets is illustrated by the high-resolution transmission electron microscopy (HR-TEM) image in Figure 1. The concept that was introduced by Shibata et al.[1] will be exploited to create nanosheet building blocks.

In a second route, embedded nano-sized objects will be made by pulsed laser deposition (PLD) from a single target comprising two immiscible phases. The concept was illustrated by Zheng and co-workers[3] and is illustrated in Figure 2. The authors showed that they could produce CoFe2O4 nanopillars embedded in a BaTiO3 matrix.

Figure 1

Figure 2

Figure 1: Cross-sectional HR-TEM image of a Pr0.002(Ca0.6Sr0.4)0.997TiO3 film on a Ca2Nb3O10 nanosheet seed layer supported by a glass substrate. Adapted from [2]; © 2009, American Chemical Society

Figure 2: Schematic representation of the alignment of a spinel (CoFe2O4; top left) and perovskite (BaTiO3; top right) phase on a SrRuO3 (100)p substrate (bottom) [a] and the resulting nanocomposite film [b]. Adapted from [3]; © 2004, AAAS

In the second phase of the project, we will be aiming to build spatially organized assemblies from the different building units. These assemblies should exhibit collectively one or more functional properties that are not a priori present in the building blocks themselves, but rather emerge from the shape, properties, spatial arrangement and mutual interaction of the building units.