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An amphiphilic electron-deficient (n-type) perylene diimide has been synthesized and characterized. The diimide contains a hydrophobic long chain on one end and a hydrophilic ethoxy chain on the other. The self-assembly of this molecule in polar and nonpolar solvents has been demonstrated by concentration- and temperature-dependent absorption and fluorescence spectroscopies. Analysis of the spectral change for the aggregates shows typical J-aggregates for structures precipitated from polar solvents and H-aggregates for structures precipitated from nonpolar solvents. SEM and TEM micrographs and a suggested packing scheme, compatible with the formation of nanostrips in nonpolar solvents and nanofibers in polar solvents, are presented.

Trace amounts of Hg2+ are detected by using a microcantilever coated with gold. The microcantilever undergoes bending due to accumulation of Hg2+ on the gold surface. It is found that a concentration of 10(-11) M Hg2+ can be detected using this technology. Other cations, such as K+, Na+, Pb2+, Zn2+, Ni2, Cd2+, Cu2+, and Ca2+ have little or no effect on the deflection of the cantilever. The selectivity of the Hg2+ sensor could be improved by coating the gold surface of microcantilever with a self-assembled monolayer of a long-chain thiol compound.

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Micrometer-long nanobelt and nanowires from deposition of perylenediimide (PTCDI) and naphthalenediimide (NPDI) in glass substrates from the gas phase were demonstrated. The electron diffraction pattern of PTCDI shows that the PTCDI molecules are oriented with their long axis perpendicular to the belt and the pi-pi stacking direction parallel to the belt. No crystal structure of the NPDI nanowires was observed. This is a new strategy to assemble organic molecules to nanostructures, typically for those having very low solubility in solvents. The approach would completely eliminate the effect of side chains.

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