Phyto-inspired silica nanowires: characterization and application in lipase immobilization

Silica nanostructures were phyto-fabricated on different surfaces by using pomegranate (Punica granatum) leaf extracts. On zinc films, nanowires were obtained. On other surfaces such as silica, alumina, zinc oxide, and glass, spherical aggregates, cubic assemblies, microflakes, and acicular structures, respectively, were observed. The nanowires developed on Zn surfaces were characterized by scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), photoluminescence, and Fourier transform infrared (FTIR) spectroscopic analysis. XRD profiles displayed peaks at 2.4, 4.9, and 12.1° indicating the presence of silica nanostructures. When excited at 340 nm, the reaction mixtures displayed a characteristic blue luminescence at 404 nm. FTIR spectra showed the existence of Si-OH and Si-O-Si bonds. The nanowires were functionalized with amine groups and used for the covalent immobilization of Candida rugosa lipase. The immobilized enzyme displayed better pH and temperature stability and retained 80% activity after 20 cycles. This paper highlights a novel route for the phyto-mediated growth of silica nanowires on Zn surfaces, their characterization and effective use as a matrix for enzyme immobilization.