Kinetic Precipitation of Solution-Phase Polyoxomolybdate Followed by Transmission Electron Microscopy:A Window to Solution-Phase Nanostructure

摘要

This study aimed to elucidate the structural nature of the polydis-perse,nanoscopic components in the solution and the solid states of partially reduced polyoxomolybdate derived from the {Mo_(132)} keplerate,{(Mo)Mo_5}_(12)-{Mo_2 acetate}_(30).Designer tripodal hexamine-tris-crown ethers and nanoscopic molybdate coprecipi-tated from aqueous solution.These mi-crocrystalline solids distributed particle radii between 2-30 nm as assayed by transmission electron microscopy (TEM).The solid materials and their particle size distributions were snap shots of the solution phase.The mother liquor of the preparation of the {Mo_(132))keplerate after three days revealed large species (r=20-30 nm)in the co-precipitate,whereas {Mo_(132)} keplerate redissolved in water revealed small species (3-7 nm)in the coprecipitate.Nanoparticles of coprecipitate were more stable than solids derived solely from partially reduced molybdate.The TEM features of all material analyzed lacked facets on the nanometer length scale;however,the structures diffracted electrons and appeared to be defect-free as evidenced by Moire patterns in the TEM images.Moire patterns and size-invariant optical densities of the features in the micrographs suggested that the molybdate nanopar-ticles were vesicular.