Supporting Information. for. Advanced Materials, adma Wiley-VCH 2007

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1 Supporting Information for Advanced Materials, adma Wiley-VCH Weinheim, Germany

2 Supporting Information Polarization Properties and Switchale Assemly of Nanorods Somorata Acharya 1, Asit B. Panda 2, Shlomo Efrima 2, and Yuval Golan 1 * 1 Department of Materials Engineering; 2 Department of Chemistry; Ilse Katz Center for Meso and Nanoscale Science and Technology, Ben-Gurion University, Beer-Sheva, Israel Counts 600 C a KeV Counts C KeV Elements Weight % Atom % Ordered rods Random Rods Figure S1. EDS spectra of (a) wurtzite ordered rods () zinc lende random rods. The weight and atom percentage of and in ordered and random rods are listed, respectively. Both spectra were otained using a JEM-2010 TEM equipped with a Noran EDS microanalysis system. 1

3 00.2 Intensity (a.u.) Figure S2. (a) Powder X-ray diffraction pattern of ordered rods (red curve) and random rods (lue curve). a Figure S3. lected area electron diffraction (SAED) otained from (a) ordered rods and () random rods. The calculated d-spacings indicate Miller indices corresponding to the WZ modification of for the ordered rods and ZB modification of for the random rods. The strongest intensity of the 00.2 reflection in (figure S3a) and 111 reflection in (figure S3) indicate a preferred orientation in which the rods are aligned with their long axis parallel to the sample plane; the ordered WZ rods are oriented with the [00.1] WZ crystallographic axis parallel to the long axis of the rods, while the random ZB rods are oriented with the [111] ZB crystallographic axis parallel to the long axis of the rods. The road ring of smallest diameter (figure S3a) is composed of a triplet of three rings that correspond to the 10.0, 00.2 and 10.1 reflections. This characteristic triplet serves for positive identification of the WZ structure. The strong intensity of the 00.2 reflection vs. the 10.1 reflection (which is the strongest reflection in JCPDS powder diffraction file # for WZ ) in the SAED pattern indicates the aove mentioned preferred orientation with a [10.0] zone axis in which oth (00.2) and (11.0) planes are in diffraction 2

4 conditions. The zone axis for the SAED pattern of the ZB structure in (figure S3) is [110] in which oth (111) and (220) planes are in diffraction conditions. Finally, we note that due to the similar spacing of (00.2) WZ and (111) ZB, some amounts of WZ in the pattern shown in figure S3 and likewise, some amounts of ZB in the pattern shown figure S3a, cannot e ruled out. Supportively, HRTEM of the ordered WZ and random ZB rods (not shown) depict well-resolved lattice planes with inter-planar distances of 0.32±0.07 and 0.327±0.07 nm, respectively corresponding to the (00.2) and (111) planes of the WZ and ZB structure. Intensity (a.u.) Asorance (a.u.) Wavelength (nm) Wavelength (nm) Figure S4. Room temperature photoluminescence spectra of ordered rods (red curve) and random rods (lue curve) in dichloromethane with excitation at 370 nm. Deconvolution for ordered rods shows a strong emission and at ~ 436 nm (and-edge emission), and two surface or defect ands at 500 nm and 546 nm (lack curves). Insert - UV-vis asorption spectra of ordered (red curve) and random rods (lue curve) dispersed in dichloromethane. 3

5 a 30 µm 30 µm c d 30 µm 1 mm Figure S5. Suspensions of nanorods in toluene oserved in an optical microscope etween crossed polarizers. The parallel ars on the sides of the images represent the position of the graphite electrodes: (a) Before applying an electric field showing only random irefringent sumicron sized spots () The electric field reorders the rods, forming microstrings along the direction of electric field (c) A mild shaking of the cell destroys the long-range ordering and the clusters revert to its randomly aligned configuration into smaller clusters (d) large area video image of the cell with microstrings exposed to unpolarized white light. 4

6 a Figure S6. TEM images showing (a) part of microstrings otained using 0.4mg/2ml suspension, with the ordered rods clearly resolved within the microstring at different magnifications. The white circles denote the exact places of higher magnification images. () Another microstring with aligned ordered rods within. The white oundaries denote the deviations from the common alignment of the ordered rods in the direction of electric field. 5

7 Figure S7. TEM of control sample deposited without applying an electric field, showing random orientation of the nanorod clusters. 6