Inorganic nanoclusters dispersed in organic matrices are of importance to a number of emerging technologies. However, obtaining useful properties from such organic-inorganic composites often requires high concentrations of well-dispersed nanoclusters. In order to achieve this goal the chemistry of the particle surface and the matrix must be closely matched. This is based on the premise of minimization of the interfacial free energy; an excess of free energy will cause phase separation and ultimately aggregation. Thus, the optimal system is one in which the nanoclusters are stabilized by the same molecules that make up the encapsulant. Yet, the organic matrix is typically chosen for its bulk properties, and therefore may not be amenable to chemical modification. Also, the organic-inorganic interface is often critical to establishing and maintaining the desired nanocluster (and hence composite) properties, placing further constraints on proposed chemical modification. For these reasons we have adopted the use of aminefunctionalized trimethoxysilanes (ormosils) as an optical grade encapsulant. In this work, we demonstrate that ormosils can produce beneficial optical effects that are derived from interfacial phenomena, which can be maintained throughout the encapsulation process.
Single layer transition metal sulfides (SLTMS) such as MoS{sub 2}, WS{sub 2}, and ReS{sub 2}, play an important role in catalytic processes such as the hydrofining of petroleum streams, and are involved in at least two of the slurry-catalyst hydroconversion processes that have been proposed for upgrading heavy petroleum feed and other sources of hydrocarbon fuels such as coal and shale oils. Additional promising catalytic applications of the SLTMS are on the horizon. The physical, chemical, and catalytic properties of these materials are reviewed in this report. Also discussed are areas for future research that promise to lead to advanced applications of the SLTMS.
Powder phosphors of ZnS:Ag,Cl coated with SiO{sub 2} (22 or 130 nm nanoparticles), SnO{sub 2} or Al{sub 2}O{sub 3} showed different cathodoluminescent (CL) brightness versus time (temporal CL quenching) behavior as compared to noncoated phosphors. At high current density (e.g., 300-800 {micro}A/cm{sup 2}), the CL emission intensity of coated ZnS:Ag,Cl decayed over the first {approx}15 s of electron beam irradiation, which was postulated to result from a large concentration of nonradiative surface centers generated during surface modification of the phosphor, and from localization of generated electrons at the surface due to primary beam-induced internal electric fields. During the first {approx}15 s of excitation, generated electrons are postulated to be redistributed by this induced internal electric fields, resulting in increased nonradiative surface recombination between electrons and holes. The formation of a nonradiative surface layer either from electron-stimulated surface chemical reactions on coated or from heat treatment of noncoated ZnS:Ag,Cl powder phosphors were shown to affect temporal CL quenching.
This SAND report is the final report on Sandia's Grand Challenge LDRD Project 27328, 'A Revolution in Lighting -- Building the Science and Technology Base for Ultra-Efficient Solid-state Lighting.' This project, which for brevity we refer to as the SSL GCLDRD, is considered one of Sandia's most successful GCLDRDs. As a result, this report reviews not only technical highlights, but also the genesis of the idea for Solid-state Lighting (SSL), the initiation of the SSL GCLDRD, and the goals, scope, success metrics, and evolution of the SSL GCLDRD over the course of its life. One way in which the SSL GCLDRD was different from other GCLDRDs was that it coincided with a larger effort by the SSL community - primarily industrial companies investing in SSL, but also universities, trade organizations, and other Department of Energy (DOE) national laboratories - to support a national initiative in SSL R&D. Sandia was a major player in publicizing the tremendous energy savings potential of SSL, and in helping to develop, unify and support community consensus for such an initiative. Hence, our activities in this area, discussed in Chapter 6, were substantial: white papers; SSL technology workshops and roadmaps; support for the Optoelectronics Industry Development Association (OIDA), DOE and Senator Bingaman's office; extensive public relations and media activities; and a worldwide SSL community website. Many science and technology advances and breakthroughs were also enabled under this GCLDRD, resulting in: 55 publications; 124 presentations; 10 book chapters and reports; 5 U.S. patent applications including 1 already issued; and 14 patent disclosures not yet applied for. Twenty-six invited talks were given, at prestigious venues such as the American Physical Society Meeting, the Materials Research Society Meeting, the AVS International Symposium, and the Electrochemical Society Meeting. This report contains a summary of these science and technology advances and breakthroughs, with Chapters 1-5 devoted to the five technical task areas: 1 Fundamental Materials Physics; 2 111-Nitride Growth Chemistry and Substrate Physics; 3 111-Nitride MOCVD Reactor Design and In-Situ Monitoring; 4 Advanced Light-Emitting Devices; and 5 Phosphors and Encapsulants. Chapter 7 (Appendix A) contains a listing of publications, presentations, and patents. Finally, the SSL GCLDRD resulted in numerous actual and pending follow-on programs for Sandia, including multiple grants from DOE and the Defense Advanced Research Projects Agency (DARPA), and Cooperative Research and Development Agreements (CRADAs) with SSL companies. Many of these follow-on programs arose out of contacts developed through our External Advisory Committee (EAC). In h s and other ways, the EAC played a very important role. Chapter 8 (Appendix B) contains the full (unedited) text of the EAC reviews that were held periodically during the course of the project.