Proto-IRG: Nanoparticle-Based Materials

Engineered nanoparticles present a wide range of opportunities for the synthesis and assembly of materials with entirely new electronic, optical or mechanical properties. They are of interest for materials science because their size-dependent characteristics give rise to an entirely new spectrum of materials properties. In addition, nanoparticles offer new ways of forming combinations of very disparate materials at the nanoscale through combining nanoparticles with other nanoparticles or/and other types of nanostructures. Such heterostructures are expected to enable electronic, optical and photovoltaic devices with greatly enhanced performance. Current methods of producing heterostructures still suffer from severe limitations such the need for chemical compatibility and sufficient lattice match for pseudomorphic epitaxial growth. This proto-IRG is a vertically integrated team of investigators with expertise in nanoparticle synthesis, characterization, directed nanoparticle assembly, and nanoparticle surface chemistry. Approaches include the remote synthesis of semiconductor nanocrystals, the passivation of their surfaces states in the gas or liquid phase with organic or inorganic shells, and the directed or stochastic assembly of nanoparticles as a novel way to form heterostructures using virtually any combination of materials. The proto-IRG focuses on questions such as whether electronic and optical properties of nanoparticles are determined by the particle surface or by bulk properties, whether the properties of the particle surface can be modified by organic or inorganic passivation of interface states, and whether heterojunction interfaces can be tailored through organic or inorganic passivation of interface states. The current research emphasis of the group is on nanoparticle-based materials for photovoltaic applications, for solid-state lighting, and for novel electronic devices.

The principal investigators and their primary areas of expertise are:

• Uwe Kortshagen, program leader - Nanoparticle synthesis, electronic materials
• Eray Aydil - Materials synthesis, surface chemical characterization
• Stephen Campbell - Electronic properties and characterization
• Heiko Jacobs - Nanoparticle directed assembly
• Xiaoyang Zhu - Surface chemistry, organic particle passivation

The collaborators are:

• William Gerberich (UMN) - Mechanical characterization and properties
• Steve Girshick (UMN) - Nanoparticle synthesis, superhard materials
• David Norris (UMN) - Photo-physical properties of quantum dots