ELECTRONIC-PROPERTIES OF SINGLE AU NANOCRYSTALS AND SYNTHESIS OF 1-DIMENSIONAL NANOCRYSTAL ARRAYS

The current-voltage characteristics of citrate- and octanethiol-capped Au nanocrystals assembled on planar Au substrates under ambient condi tions in air and in solution are reported. We have found that single e lectron tunneling (SET) behavior is observed for citrate-capped Au cry stals in air. In high dielectric media, however, SET is only seen for nanocrystals protected by the hydrophobic alkane ligands and not for t he relatively bare citrate-capped nanocrystals. In addition, we report a new strategy for assembling these nanocrystals into spatially well- organized 1-dimensional (1D) arrays. The method involves trapping the crystals inside 20 nm diameter pores of porous filtration membranes. T he 1D linked nanocrystals confined inside the membrane pores were char acterized by ultraviolet-visible spectroscopy. ''Shrink-wrapping'' the nanocrystals with the organic conductive polymer polypyrrole or coval ently linking the particles with alkyldithiols and subsequent dissolut ion of the membrane provided a suspension suitable for characterizatio n by transmission electron microscopy. These studies are important in determining the role of spatial arrangement and chemical environment-o n the electronic properties of this important class of crystalline mat erial. (C) 1998 Elsevier Science Ltd.