RNA-Templated Fluorescent Zn/PbS (PbS + Zn2+) Supernanostructures

Synthesis of novel Zn/PbS (Zn2+ + PbS) fluorescent nanostructures of varied morphology and dimension has been reported. Zn2+ passivates the surface of RNA-templated PbS by binding to the specific sites of RNA through PO2- and purine bases and controls the dynamics of charge carriers, electronic properties, and growth of PbS in the nanocomposite. For a typical molar ratio of Pb/S = 2, the addition of 2 x 10(-3) mol dm(-3) of excess Zn2+ results in one-dimensional growth of spherical particles of RNA-mediated PbS to form nanofibers via several metastable self-assembled supernanostructures. The addition of Zn2+ enhances the fluorescence intensity of the 680 nm band. The nanofibers produced upon aging display a strong narrow emission band (fwhm <= 80 nm) at 680 nm having a quantum efficiency of 12 +/- 0.2%. An increase in the fluorescence quantum efficiency with increasing Zn2+ is also evidenced by a drastic increase in fluorescence lifetime from 0.06 mu s in its absence to 0.23 mu s for the colloids containing 2 x 10(-3) mol dm(-3) Zn2+, which is further increased to 0.27 mu s upon aging. These studies demonstrate a correlation between the morphology of nanostructures and their electronic properties.