Chapter 8 - Magnetic Multicomponent Heterostructured Nanocrystals

Inorganic nanomaterials represent unique solid-state platforms on which unusual optoelectronic, magnetic chemical, and catalytic properties can be manipulated, tuned, and even allowed to coexist and exchange-couple, holding considerable potential for both fundamental studies and practical applications in optoelectronics, energy technologies, catalysis, and biomedicine. Among the available synthetic approaches, colloidal techniques stand out as powerful routes to nanocrystals with programmable composition, crystal structure, geometry, and surface functionalities. Knowledge of thermodynamic and kinetic growth conditions and processes underlying monophasic nanocrystal evolution in liquid media has triggered significant advances in these fabrication tools, paving the way to increasingly sophisticate multifunctional hybrid nanoarchitectures, in which sections of different materials are assembled together as free-standing, easily processable all-inorganic nanoheterostructures. In this chapter we will illustrate recent progress made in the wet-chemical development and characterization of last-generation breeds of colloidal heterostructured nanocrystals (HNCs), in which distinct material modules are interconnected via direct bonding (heteroepitaxial) interfaces in elaborate onion-like or oligomer-type topologies. Emphasis will be put on HNCs that entail at least one magnetic material component, combined with semiconductors and/or plasmonic metals as a means of generating enhanced, unconventional magnetic behavior as well as diversified properties and capabilities. Diverse synthetic strategies, all based on manipulation of seeded-growth techniques, will be described and interpreted within the framework of the relevant heteroepitaxial deposition mechanisms that enable topological selection of HNCs with selected spatial configurations.