A holy grail of nanotechnology is to design and build a material with some desirable property by engineering the atomic structure at the nanoscale. A huge impediment to this is the nanostructure problem: the fact that the established quantitative methods for determining atomic structure fail for nano-sized objects. This project addresses this problem with a collaboration of experiment and theory. The experiments utilize the intense beams of x-rays and neutrons available at US national user facilities combined with novel computational approaches for extracting reliable structural information from the data. In addition the local structure of intermediate states will be studied using ultra-fast femtosecond time-resolved electron diffraction, coupled to the same computational infrastructure, allowing us for the first time to probe quantitatively the local structure of excited states of nanoparticles. In this study a number of scientifically and technologically interesting materials will be studied, including quantum-dot nanoparticles and phase-change materials used in writable CD and DVDs. However, the theoretical and methodological developments will be made available to the wider scientific and educational community in the form of freely available software so the methods can be widely applied. In addition to training graduate and undergraduate students in state-of-the-art research, nanotechnology will be taken to the classroom in grades 6-12 and new hands-on nanotechnology modules will be built in collaboration with Everett High School, an inner city Lansing high school. A new curriculum and course content for an AP course will be developed with their active participation. This project is co-supported by the Condensed Matter Physics and Solid State Chemistry programs.
A holy grail of nanotechnology is to design and build a material with desirable properties by engineering the atomic structure at the nanoscale. A huge impediment to this is the nanostructure problem: the fact that the established quantitative methods for determining atomic structure fail for nano-sized objects. This collaborative project addresses this by using novel approaches for analyzing and modeling x-ray and neutron scattering data from nanomaterials. The data will be Fourier transformed to obtain the atomic pair distribution function (PDF) which will be modeled using novel approaches that will be developed such as encoding chemical information as geometrical constraints in the model. The analysis will be extended to electron diffraction data and combined with ultrafast techniques to study local structure quantitatively on femtosecond time-scales. The systems under study include novel electronic and optical materials such as low-dimensional charge-density wave tellurides, quantum-dot nanoparticles and phase change materials that are used in writable CDs and DVDs. The methods developed here will be made available to the broad community of nanotechnology scientists through training and free software. In addition to training graduate and undergraduate students in state-of-the-art research, nanotechnology will be taken to the classroom in grades 6-12 and new hands-on nanotechnology modules will be built in collaboration with Everett High School, an inner city Lansing high school. A new curriculum and course content for an AP course will be developed with their active participation. This project is co-supported by the Condensed Matter Physics and Solid State Chemistry programs.
A holy grail of nanotechnology is to design and build a material with some desirable property by engineering the atomic structure at the nanoscale. A huge impediment to this is the nanostructure problem: the fact that the established quantitative methods for determining atomic structure fail for nano-sized objects. This project addressed this problem with a collaboration of experiment and theory. The experiments utilized the intense beams of x-rays and neutrons available at US national user facilities combined with novel computational approaches for extracting reliable structural information from the data. The local structures of technologically important materials such as PbTe, PbSe, PbS and CeTe3, were studied using pair distribution function analysis, ultra-fast femtosecond time-resolved electron diffraction. The PbTe, PbSe, PbS are the basis of highly efficient thermoelectric materials. Thermoelectric materials are used to convert waste heat to useful electricity. In the case of CeTe3 time-resolved electron diffraction was coupled to a computational infrastructure that allowed us for the first time to probe quantitatively the local structure of excited states of nanoparticles. In this study a number of scientifically and technologically interesting materials were investigated, including quantum-dot nanoparticles and phase-change systems. Our findings have significant impact on the fundamental understanding of the unusual physical properties of PbTe, PbSe and PbS such as the very low thermal conductivity. Such low thermal conductivity greatly increases the conversion efficiency of thermoelectric materials.
