Inter-American Materials Collaboration: Correlating Erbium

1. Inter-American Materials Collaboration: Correlating Erbium Structure with Host Geometry in Doped Nanocrystals and Nanowires Jeff Coffer, TCU,DMR-0303366 Semiconducting nanowires (NWs) are interesting and useful materials due to their unique geometry and resultant structural & electronic confinement. In addition to successfully synthesizing a new diverse series of crystalline NWs comprised of silicon (Si), germanium (Ge), and Erbium (Er), this year we have also accomplished : •Dual wavelength emitters: To complement the structures described above (comprised of tech-familiar semiconductors Si and Ge), we have also successfully synthesized a new series of hybrid photonic zinc oxide (ZnO) nanowires possessing an erbium coating along the surface of the wire; these new materials expand the portfolio of available optical materials, as we have now produced a structure that emits efficiently both in the visible and near infrared. •Silicon nanowires are non-toxic: Given the common use of lanthanide containing substances in MRI imaging diagnostics and for possible therapeutic relevance, we have assessed the cytotoxicity of our Si and Ge nanowires, along with the Er-doped analogs, via fibroblast cell viability and proliferation studies in vitro. The results are overwhelmingly positive. •EXAFS Measurements in Brazil: With the aid of our Brazilian collaborators at UNICAMP and active participation by TCU undergraduate and graduate students, we have measured the erbium structural environment for dopant centers located within these semiconducting nanowire motifs through the use of Extended X-Ray Absorption Fine Structure (EXAFS) measurements at the Brazilian National Synchrotron Light Laboratory (LNLS) at Campinas. Erbium-doped Zinc oxide nanoribbons Optical image of Si NWs & fibroblasts, a cell type common to connective tissues.

2. Inter-American Materials Collaboration: Correlating Erbium Structure with Host Geometry in Doped Nanocrystals and Nanowires Jeff Coffer, TCU,DMR-0303366 Educational Activities •Prof. Leandro Tessler of the Dept. of Applied Physics of the State Unversity of Campinas (UNICAMP) and one of his graduate students, Danilo Mustafa, visited TCU in February for two weeks, presenting seminars, interacting with students, analyzing data, and discussing plans for additional research directions. • Mr. Mustafa then remained with the Coffer group at TCU for an additional four months, engaging in intensive hands-on experience in Er-doped nanowire and nanocrystal synthesis of great value to his doctoral research in Brazil. During his stay, Danilo initiated a new project involving the fabrication and characterization of some novel Er-doped ZnO nanowires. • In June, TCU undergraduate Chemistry major Scott Dunkle and two Chemistry graduate students (Dongmei Fan, Alex Sereguine) traveled to Brazil in order to participate in EXAFS measurements at the Brazilian National Synchrotron Light Source in Campinas, Sao Paulo. These students collected data on a broad array of Er-doped surface modified Si nanocrystals, Er-doped Ge NWs, and Er-doped SiGe NWs, along with some novel Erdoped ZnO nanowires fabricated in the Coffer lab by Mr. Mustafa of UNICAMP. Top(L-R): Scott Dunkle (TCU), Ji Wu (TCU), Danilo Mustafa (UNICAMP), Ke Jiang (TCU); Bottom (L-R): Alex Serguine (TCU), Jeff Coffer (TCU), Leandro Tessler (UNICAMP), Melanie Whitehead (TCU).