Structural Characterizations of Biogenic Germanium Oxide Nanospheres
EMSL Project ID
2647
Abstract
Background Marine organisms are inspirational sources of nanomaterials. It is well known that many marine organisms intricately incorporate inorganic elements such as calcium and silicon into structural features, e.g. shells, skeleton, and cell walls, with both nanometer-scale and micrometer-scale precision. Diatoms are a particularly prolific class of microalgae (the Bacillariophyceae) capable of silicon biominerization. Diatoms possess a unique ability to actively assimilate soluble silicon and biologically polymerize it into silica nanospheres of less than 50 nm diameter within the cell. These silica nanoparticles then assemble into cell wall components that possess a myriad of shapes, each exquisitely organized at the micrometer scale. We (Greg Rorrer and Chih-hung Chang) are exploring the possibility of using marine diatoms as a nanofactory for the production of Germanium Oxide, (Silicon, Germanium) oxide nanospheres. Objectives and Approach It is proposed to use the JEOL 2010 high resolution TEM housed in the Environmental Molecular Sciences Laboratory (EMSL), Pacific Northwest National Laboratory through the user program. The biogenic nanoparticles will be extracted from the silicified diatom cell wall using Oxygen plasma ashing. These extracts will be prepared for TEM investigation by simply dispersed the nanoparticles on copper grid coated with SiO films. Electron diffraction techniques including Selected Area Diffraction (SAD), micro-diffraction, and convergent beam electron diffraction will be used to study the long-range order of the nanoparticles. SAD will first be performed to obtain electron diffraction patterns from an ensemble of nanoparticles. The structure of individual nanocrystal will be studied through electron microdiffraction and nanodiffraction using a focused electron beam. The JEOL 2010 has a spatial resolution of 0.194 nm and a minimum electron bean size of 0.5 nm. This feature will allow us to do nanodiffraction studies on sub-nanometer nanoparticles. The properties of nanosized crystals depend on their geometrical shapes. It is therefore important in our experiment to characterize the shape as well as the number and composition of each nanoparticles. For this purpose, real-space images of these nanoparticles will be obtained using a few imaging techniques, including both bright field and dark field, and High Resolution TEM (HRTEM). Bright field and dark field imaging will provide the information on the shape of a particle. For example, weak beam imaging technique will be used to construct a three dimensional model of the particle. HRTEM will complement with atomic resolution images. Furthermore, JEOL 2010 will allow us to obtain compositional information on nanosized domain using the EDS system.
Project Details
Project type
Exploratory Research
Start Date
2002-10-15
End Date
2004-11-01
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members