AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP11
Valence-Band and Core-Level X-Ray Photoelectron Spectroscopy of Lead Sulfide Nanocrystal/Polymer Composites

Tuesday, November 14, 2006, 6:00 pm, Room 3rd Floor Lobby

Session: Surface Science Poster Session
Presenter: D.J. Asunskis, University of Illinois at Chicago
Authors: D.J. Asunskis, University of Illinois at Chicago
L. Hanley, University of Illinois at Chicago
Correspondent: Click to Email
Lead salt nanocrystals have been the subject of intense recent interest due to their potential applications in photovoltaics, near infrared sensors, and other optoelectronic devices. However, relatively few studies have used photoemission to probe the electronic structure of these novel nanomaterials. Valence-band and core-level X-ray photoelectron spectroscopy (XPS) are therefore used to probe different lead sulfide (PbS) nanocrystal-polymer nanocomposites. Composite materials are prepared by trapping monodisperse 3 and 10 nm lead sulfide nanocrystals in two polymers, the non-conducting polymer, polystyrene, and the conjugated polymer, poly (2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylene vinylene or MEH-PPV. Additional composites with polydisperse lead sulfide nanocrystals were synthesized by growing the particles in the presence of MEH-PPV and poly (vinyl alcohol). These materials are initially characterized by UV/Vis optical absorption and transmission electron microscopy to monitor the particle size in the composites. Monochromatic XPS with charge neutralization is then used to collect both core-level and valence-band spectra. The composites with monodisperse particle sizes exhibit a shift to lower energy of the highest occupied molecular orbital as the lead sulfide particle size increases from 3 to 10 nm. Oxidation of the sulfur content in the particles by air during fabrication and transport was minimal as evident by the small contribution of oxidized sulfur in the XPS spectra. The core level XPS results also show additional states in the lead core XPS regions that change as the particle size changes. The monodisperse composites are compared to the other composites synthesized having varied particle size, showing the effects of size variance and polymer/particle bonding in the core level and valence band XPS spectra.@footnote 1@ @FootnoteText@ @footnote 1@This work is supported by the U.S. Department of Defense.