PHILADELPHIA - Collaboration by chemists, physicists and materials scientists at the University of Pennsylvania has created a simple and inexpensive method to rapidly grow centimeter-scale membranes of binary nanocrystal superlattices, or BNSLs, by crystallizing a mixture of nanocrystals on a liquid surface.
The study demonstrates a new and spontaneous way to grow long-range-ordered BNSL membranes with rigorous control of nanocrystal size, shape and concentration by combining two types of nanocrystals and assembling them during a drying stage at the surface of a liquid under normal conditions.
The method overcomes several limitations of the existing assembly strategies and produces large, free-standing membranes that can be transferred to any desired substrate such as silicon wafers, glass slides and plastic substrates, allowing the nanocryatalline films to be introduced at any stage in the device fabrication process.
The team demonstrated the potential for integrating these novel materials by growing millimeter-scale superlattice membranes containing iron oxide nanocrystals of two different sizes and incorporating the membranes into magnetoresistive devices. Measurements showed that the magnetoresistance of the resulting device was dependent on the structure of the BNSL and therefore controllable.
The physical properties intrinsic in these nanocrystals -- nanometer sized crystalline building blocks offer a modern twist on the studies of interfacial assembly that reach as far back as Penn founder Benjamin Franklin and his studies of oil spreading on water in the 1770s.
Single and multi-component nanocrystal films are already under intense investigation by researchers as enablers of novel optical technologies that range from low-cost solar cells, light-emitting diodes and photo detectors and also in electronic systems that include field-effect transistors and solid-state thermoelectric coolers and generators
|Contact: Jordan Reese|
University of Pennsylvania