Experimental details
All solvents and reagents were purchased from Sigma-Aldrich or
Strem Chemicals and used as received. Scanning electron
microscopy (SEM) was done using a Weiss Gemini Ultra-55
Analytical Scanning Electron Microscope operated at 5 kV.
Transmission electron microscopy (TEM) was done using
a JEOL 2100-F Field-Emission Analytical Transmission Electron
Microscope operated at 200 kV. X-ray diffraction was
performed on samples prepared on silicon substrates using
a Bruker-AXS D8 with a general area detector and Cu Ka
radiation (l ¼ 1.54 A). UV-vis absorbance measurements were
made using a Shimadzu UV-3600.