Lamellar Micelles as Templates for the Preparation of Silica Nanodisks

We have reported earlier that silica nanodisks are formed by the reverse micelle sol-gel (RMSG) method, from ternary Aerosol OT (AOT)/n-heptane/water mixtures. These nanodisks are formed from the ternary mixtures with higher water contents and containing a significant concentration of FeCl3. Such mixtures undergo a phase separation. The present work seeks to identify the origin of these nanodisks. They are found to be produced from the lower, water-rich layer and not from the upper, oil-rich layer or from the interfacial region. Further, upon increasing the water content by a factor of 10, the phase separation is achieved in the absence of the salt as well. In the next step, the naodisks are observed to form from concentrated aqueous AOT solutions, with no involvement of organic solvents. Polarized optical microscopy and infrared studies reveal the occurrence of lamellar AOT micelles in these media. These micelles act as the templates for the nanodisks. This phenomenon paves the way for the soft chemical preparation of nanodisks in the aqueous phase, without the need of using salt or organic solvents.