Molecular Structure for Smart Materials.

摘要

This project has developed new electron diffraction methods for determining the structure of organic sensors and detectors, including a colorimetric diacetylene phospholipid which changes color when exposed to toxins, and a new hard covalent carbonate. We are concerned with radiation- sensitive molecules which cannot be crystallized for analysis by X-ray crystallography, and with new nanostructured organics which do not form large enough single crystals for X-ray analysis. Since the main problem is radiation damage, we have studied this problem in detail. The use of low electron energies to reduce radiation damage has proven effective. We have obtained the first transmission electron diffraction patterns at a beam energy below the carbon K - shell ionization energy (285 eV). We have designed and constructed a field- emission point-projection electron microscope (PPM), a facility for making coated nanotip field emitters, a low energy electron diffraction camera, and facilities for making thin organic films by the Langmuir Bludgett and other methods. The PPM has successfully given nanometer-resolution coherent electron holograms and reconstructed images, at 200 eV, of Tobacco Mosaic Virus. In addition, we have solved a new organic crystal structure whose sub-micron grain- size prevented it being solved by any other method. This material holds promise as a hard, light, optical material. In summary, we now have the hardware and software in place to image useful organic molecules which do not form large enough crystals for conventional analysis.