1.All steps of the synthesis were performed using double distilled water under nitrogen atmosphere to exclude airborne CO2. Concentrated NaOH (_20 M) stock solutions were prepared from a.r. grade solid NaOH (Spectrum 3D) and their carbonate content was minimised.2. The exact concentration was determined through accurate density measurement.3. The solution was stored in an airtight, caustic resistant Pyrex bottle.4. This solution was used for making the 3 M NaOH solution actually used in the synthesis.5. CaCl2 (Molar Chemicals, puriss), iron chloride (FeCl3_6H2O, Molar Chemicals, puriss special) were used without further purification.