When 10:30 AM - 11:30 AM Jan 08, 2016
Where 1670 Beyster Building
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Luminescent Boron Materials for Imaging and Sensing

Cassandra L. Fraser
Departments of Chemistry and Biomedical Engineering

Luminescent boron -diketonate dyes are known for their intense fluorescence, 2-photon absorbing capability, and environmentally sensitive emission. They also display unusual optical properties in the solid state. For example, difluoroboron dibenzoylmethane poly(lactic acid) analogues exhibit both intense fluorescence and long-lived room temperature phosphorescence. When fabricated as nanoparticles, these simple, dual-emissive biomaterials serve as optical probes for cell biology and as ratiometric tumor hypoxia imaging agents, with impressive combined spatial and temporal resolution. Oxygen imaging is also relevant in wounds, tissue engineering, vascular, brain and other contexts. Difluoroboron -diketonate dyes also show surprising properties as molecular solids. For example, the difluoroboron complex of avobenzone, a simple sunscreen ingredient, has narrow bandwidth green, cyan, or blue emission depending on the solid form. Furthermore, the emission color changes when crystals are crushed or thin films are scratched or gently rubbed. Surprisingly, for thin films, the mechanochromic luminescence is reversible. For the avobenzone complex, regions where force is applied turn yellow but return to the original green-blue background color within minutes at room temperature or seconds with heating. The writing-fading process may be repeated many times. These simple Scratch the Surface InksTM show promise as mechanical sensors and rewritable surfaces. They have even inspired creative works in music, art and design. Progress in understanding difluoroboron diketonate dye materials, tuning their properties, and their development for imaging and sensing will be presented.

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