Abstract

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.

Highlights

  • Silver nanoparticles (AgNPs) are well known for their extensive antimicrobial activity [1] and applicability in different physical fields as catalysts [2], biosensors [3], conductive adhesives [4], in water treatment [5], ink-jet printing [6], protein sensing [7] and solar cell optimization [8], etc

  • Associated Morphological Changes in Ag+ Exposed Gedaniella The morphological changes in G. flavovirens and G. mutabilis due to Ag+ stress was preliminarily confirmed by observing color change in biomass

  • It was observed that AgSiO2 nanohybrid production against AgNO3 solution is possible by using G. flavovirens and G. mutabilis as reducing agents

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Summary

Introduction

Silver nanoparticles (AgNPs) are well known for their extensive antimicrobial activity [1] and applicability in different physical fields as catalysts [2], biosensors [3], conductive adhesives [4], in water treatment [5], ink-jet printing [6], protein sensing [7] and solar cell optimization [8], etc. The Ag particles are less stable and tend to aggregate To conquer this problem, AgNPs are needed to combine with some other nanoparticles. Ag-decorated silica nanoparticles have been synthesized by some chemical methods such as the wet-impregnation method [10] and metal-assisted chemical etching [11], which involves harmful chemicals like cetyltrimethylammonium bromide (CTAB) and hydrofluoric acid (HF). None of these techniques are environmentally friendly due to the involvement of hazardous chemicals. Only a single report regarding the synthesis of hybrid Ag-SiO2 nanodendrites by Halamphora subturgida is available [17]

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