Characterizing and Controlling Nanoscale Structure Using Layered Materials

Abstract

Interfaces are essential to the function of many biological systems, but the nanoscale structure of interfacial assemblies is, in general, not as well understood as it needs to be. We have used metal-bisphosphonate layered assemblies grown on SiOx as model systems for the investigation of local organization and defect density. These chemical systems are important in their own right as robust materials and serve as a useful model for layered membrane systems. We have used time-domain fluorescence spectroscopy and surface second harmonic generation spectroscopy to determine the extent of aggregation and investigate defect density in these assemblies. We have found that control of the substrate morphology is essential to achieve regular layer growth and that, even for relatively featured surfaces, there is a relatively low density of orientational or vacancy defects at the molecular level. This work points the way to the characterization of other, structurally complex interfacial systems.