Off-resonance Photosensitization of a Photorefractive Polymer Composite Using PbS Nanocrystals

The photosensitization of photorefractive polymeric composites for operation at 633 nm is accomplished through the inclusion of narrow band gap semiconductor nanocrystals composed of PbS. Unlike previous studies involving photosensitization of photorefractive polymer composites with inorganic nanocrystals, we employ an off-resonance approach where the first excitonic transition associated with the PbS nanocrystals lies at ~1220 nm and not the wavelength of operation. Using this methodology, internal diffraction efficiencies exceeding 82%, two-beam-coupling gain coefficients of 211 cm-1, and response times of 34 ms have been observed, representing some of the best figures of merit reported for this class of materials. These data demonstrate the ability of semiconductor nanocrystals to compete effectively with traditional organic photosensitizers. in addition to superior performance, this approach also offers an inexpensive and easy means by which to photosensitize composite materials. the photoconductive characteristics of the composites used for this study will also be considered

First-Principles Phase Diagram of Magic-Sized Carbon Clusters on Ru(0001) and Rh(111) Surfaces

Recent theoretical and experimental explorations have indicated that magic-sized clusters C-21 and/or C-21-3C play an important role in graphene chemical vapor deposition growth on both Ru(0001) and Rh(111) surfaces. However, the evolution and stability of these clusters under various conditions are not clear. Here we systemically investigated the stability and phase diagram of the probable C-21, C-21-3C, and 7-6MR clusters and their related polycyclic hydrocarbon clusters on the two metal surfaces. Taking temperature and the chemical potential of ambient H atom into account yielded phase diagrams that agree well with experimental observations