AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Silicon Nanocrystal Solvation: From Plasma to Stable Colloidal Dispersion
LANCE M. WHEELER, Uwe R. Kortshagen, University of Minnesota
Abstract Number: 243 Working Group: Synthesis of Functional Materials using Flames, Plasmas and other Aerosol Methods
Abstract Colloidal synthesis of prevailing semiconductor nanocrystals (NCs) leads to long-chain ligand termination of the surface. Though the ligands provide colloidal stability in nonpolar solvents, these ligands hinder charge transport when cast into thin films for optoelectronic device integration. Silicon offers a more abundant, non-toxic alternative to the heavily-research metal chalcogenide NC, but unreliable synthesis and inability to process from liquids has lead to stifled progress toward optoelectronic devices. Here we present a single-step nonthermal plasma synthesis method of Si NCs that allows tailoring of the NC surface to be controllably terminated with chlorine and hydrogen. We demonstrate this surface chemistry to be imperative for achieving stable dispersions of Si NCs without ligands. Choice of solvent plays an equally critical role, and we outline solvent criteria needed to achieve stable, highly concentrated dispersions of Si NCs. We employ dynamic light scattering (DLS) and UV-Vis spectroscopy to determine dispersion concentration and explore the physical and chemical characteristics of colloidal interactions using dialkyl ketones as the model system. Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy reveals acid-base interactions at the NC surface as well as intermolecular solvent interactions that lead to dense packing and ordering of solvent molecules around the Si NCs. We attribute these phenomena to a novel stabilization mechanism for nanoscale, highly concentrated dispersions—solvation. Demonstration of thin films that are continuous and crack-free validate our efforts for colloidal stability and represent a significant step toward cost-effective, roll-to-roll integration of Si NCs into optoelectronics.