SUPPORTING INFORMATION Template-free synthesis of silica ellipsoids Henan Zhang, Teresa J. Bandosz, Daniel L. Akins* Department of Chemistry The City College of New York New York, NY 10031  Author to whom correspondence should be addressed: Tel: 1-212-650-6953; Fax: 1-212-650-6848; E-mail: akins@sci.ccny.cuny.edu 1. Experimental Section 1.1 Chemicals Tetraethyl orthosilicate (TEOS, 98%) was obtained from Acros Organics; hexadecyltrimethylammonium bromide (CTAB, 99+ %) was purchased from Alfa Aesar; ethylene glycol, ReagentPlus ® (99%) was purchased from Sigma-Aldrich; Ammonium hydroxide (NH 4 OH) was purchased from Pharmco products, Inc.; and ethyl alcohol 190 proof was obtained from Decon Labs, Inc. All reagents were used without further purification. Deionized water was used in all experiments. 1.2 Synthesis A typical synthesis process was as follow: 50 mL of deionized water and 35 mL ethylene glycol (99%) were mixed; ~0.2525 g CTAB was dissolved in the prepared solvents and the mixture was vigorously stirred until clear; and then 0.842 mL ammonium hydroxide (1 M) was added. The total volume of the water and ethylene glycol was maintained at 85 ml for a series of predefined ratios. After 12 mL TEOS was slowly introduced, the reaction was held at room temperature with stirring. Following the reaction, the white precipitated was filtered, washed with 500 mL ethyl alcohol, and then dried overnight in air at ~60 ºC. Finally, the resultant white powder was calcination for 8 hrs at ~580 ºC to remove any residual CTAB, and represented the final product that was characterized as discussed below. The molar ratio of CTAB/NH 4 OH/TEOS/ethylene glycol/water was 1:1.20:77.14:897.14:3968.57, when 50 mL water and 35 mL ethylene glycol were applied. 1.3 Characterization Transmission electron microscopy (TEM, Zeiss EM 902 and JOEL JEM-2100) was performed to observe the size and the morphology of silica particles. To prepare the TEM samples, calcined silica white powders were dispersed in ethanol. A 10 μl aliquot of the silica-ethanol solution was dropped onto a carbon-coated copper grid. After evaporation of the ethanol, the sample was characterized by TEM at acceleration voltages of 80 and 200 kV. Electronic Supplementary Material (ESI) for Chemical Communications This journal is © The Royal Society of Chemistry 2011