possibly intercalated with some biopolymers and thus displayed
this XRD pattern. To investigate the possible role of the
biological molecules in the assembly of the silica nanowires,
XRD patterns of heated (70 °C for 30 min) samples were
recorded. This XRD profile displayed a variation in the
intensity, sharpness and number of peaks [Figure 4A (2)]. A
similar effect of high temperature on the XRD patterns of
siliceous spicules from a marine sponge has been reported.27 As
discussed earlier, the ordered silica structures in this sponge
were biosynthesized through periodic protein units that acted
as templates. Hence the change in the XRD profiles was
attributed to protein unfolding or the reorganization of the
siliceous ordered patterns. In the present investigation also,
certain biomolecules in the leaf extract possibly mediated
growth of the silica nanowires. Photoluminescence spectra
displayed a peak at 404 nm when excited at 340 nm (Figure
4B). Emission peaks in the range of 400−500 nm are
characteristic of amorphous silica nanowires. These have been
attributed to certain structural defects.26