Reports: AC10
46443-AC10 Synthesis of Novel Heterostructured Catalyst Materials with Nanoscale Precision
Nanocrystal heterostructures (NCHs) composed of two or more distinct crystalline phases can lead to unique combinations of properties useful in multiple areas. NCHs that exhibit directionality in their structure are of particular interest in technological applications such as energy storage and conversion and catalysis. Providing synthetic control over the spatial placement and the number of one component with respect to the other is a key challenge that needs to be overcome to enable most of these applications. However, a well-established understanding of how interfaces form and the details of the nature of the heterointerfaces (e.g. crystallographic orientation, interfacial strain, etc.) is lacking. Such information is critical in developing routes to optimizing desired morphologies of NCHs – for example, specific directionality for charge separation. One of the aspects that our efforts in anisotropic NCHs have focused on is the effects of interfacial strain on the overall morphology of NCHs.
In the case of Fe3O4/CdS NCHs where there is a large overall lattice mismatch, coincidence site lattices mainly of (111)/(111) for zinc blende CdS or (111)/(0001) for wurtzite CdS form the heterointerfaces. Even in these coincidence site lattices, there is a residual lattice mismatch and the interfacial strain increases with the size of each of the components. This increasing strain leads to limitations on the achievable size and the number of particles of the second epitaxial phase. The effect of interfacial strain is also evident in NCHs consisting of two phases that have the same crystal structure but with significant lattice mismatch. NCHs synthesized from CdSe nanorods seeds (in this case, the starting rods provide the underlying anisotropy rather than relying on coincidence lattices to induce growth in limited directions) can exhibit strain induced curvature when the growth of the second II-VI component occurs beyond the tips of the seed nanorods. These results along with properties that may be tuned with varying degree of strain, size-dependent interfacial strain may be a new and an effective route to precise tailoring of properties of nanoscale materials.
