Green synthesis of novel antioxidant luminescent silica nanoparticle embedded carbon nanocomposites from a blue-green alga

Silica nanoparticle embedded carbon 2D-nanocomposite material has been synthesized using a green procedure from a blue green alga, Scytonema guyanense, by direct pyrolysis at 600°C under inert atmosphere. The nanocomposite was characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction and energy dispersive spectroscopy (EDS). Characteristic Si-O-Si vibrational absorptions at ~720 cm-1, ~790 cm-1 and ~1080 cm-1 attested the occurrence of silica in the nanocomposite material. Transmission electron microscopy (TEM) analysis revealed five-fold multiply twinned quasi spherical silica nanoparticles (~40 nm) embedded in ~3 nm thick carbon nanoflakes. The material exhibited weak luminescence at 340 nm. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging study showed moderate antioxidant activity of the material.