Diatom Mediated Production of Fluorescent Flower Shaped Silver-Silica Nanohybrid.

Fabrication of flower-like nanostructures are gaining attention because of their high surface/volume ratio and extensive adsorption capacity. In the present investigation, flower-shaped, autofluorescent silver-silica (Ag-SiO2) hybrid nanoparticles have been fabricated exploiting diatoms as a source of nanosilica. Two different species of Gedaniella including G. flavovirens and G. mutabilis showed their efficacy in synthesizing fluorescent Ag-SiO2 nanoflowers (NFs) and nanospheres (NSs) against 9 mM silver nitrate solution, respectively. The biogenic nanoconjugate (Ag-SiO2) was characterized by Uv-vis spectroscopy, energy dispersive X-ray spectroscopy (EDS), scanning (SEM) and transmission (TEM) electron microscopy. Production of Ag-SiO2 hybrid nanoparticle was confirmed by observing both Ag and Si signals from a single nanoparticle in an EDS study. The broad and single absorption band at ~420 nm in Uv-vis spectroscopy confirmed proper miscibility and production of hybrid nanoparticles. The Ag-SiO2 nanohybrids revealed autofluorescent property under the blue light region (excitation ~450-490 nm). SEM images of particles synthesized by G. flavovirens revealed the production of microscopic flower shaped Ag-SiO2 particles with several layers of petals. A TEM study confirmed that the synthesized Ag-SiO2 NFs are variable in size with 100-500 nm in diameter. Decolorization of methylene blue after exposure to Ag-SiO2 particles confirmed catalytic activity of synthesized nanostructures. This eco-friendly method provides a new dimension in nanobiotechnology for biogenesis of such hierarchical nanostructure in a cost-effective way.