Supporting Information. for. Advanced Materials, adma Wiley-VCH 2006

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

2 Supporting Information for: Porphyrin nanofiber bundles from phase-transfer ionic self-assembly and their photocatalytic self-metallization Zhongchun Wang 1,2, Kuangchiu J. Ho 3, Craig J. Medforth 1, and John A. Shelnutt 1,2, * 1. Surface and Interface Sciences Department, Sandia National Laboratories, Albuquerque, NM Department of Chemistry, University of Georgia, Athens, GA Department of Chemistry, University of New Mexico, Albuquerque, NM Synthesis of porphyrin nanofiber bundles. Oxo-Sb(V) 5,10,15,20-tetraphenylporphyrin iodide and the sodium salts of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (free base and Cu(II), Ni(II), Ag(II), or Zn(II) complexes) were purchased from Frontier Scientific and used without further purification. Stock solutions were prepared in ultrapure water from a Barnstead Nanopure water system or in dichloromethane (HPLC grade, Aldrich) and filtered through a 0.2-µm syringe filter to remove particles. The stock solutions were stored in the dark and used within two weeks. In a typical reaction, 9 ml of an aqueous solution of [H 2 TPPS 4 ] 4- (105 M) was added to 9 ml of a dichloromethane solution of [SbOTPP] + (315 M) in a 20-mL glass scintillation vial. This mixture was vigorously shaken for 2 minutes and then stirred vigorously for 1 hour using a magnetic stirrer bar. After the stirring was stopped and phase separation occurred, strands of pink material immediately appeared in the organic phase. This material tended to float up to the interface but could be dispersed in the organic phase by gentle swirling. The sample was then stored in the dark at room temperature for further characterization. When the reaction was repeated without shaking and stirring, pink strands were found to form near the interface after about 30 minutes. This material is much larger in size (up to 1 micron in width and tens of microns in length) and has a wide range of widths and lengths (see Fig. S1). Repeating this procedure with 10-fold lower porphyrin concentrations increased the formation time for the pink strands but did not appreciably change the dimensions of the material. Characterization of porphyrin nanofiber bundles. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) were performed on a JEOL 2010 transmission electron microscope (200 kev). Scanning electron microscopy (SEM) was carried out on a Hitachi S-5200 Nano Scanning Electron Microscope operating at 1 kv. The samples for TEM analysis were prepared by pipetting 5-25 µl of the nanofiber suspension onto standard holeycarbon-coated copper TEM grids (SPI Supplies, Φ 3 mm, catalogue # 3620C-MB). The excess solvent was wicked away by a Kimwipe tissue underneath the copper grid. The grids were air dried for at least 2 hours before being loaded into the vacuum chamber of the electron microscope. The samples for both TEM and SEM imaging were not subjected to any pretreatments such as heavy-metal staining or metal/carbon coating. Samples on TEM grids were observed by SEM using a specially designed sample holder. The fluorescence images were recorded using a Zeiss LSM510 META laser scanning microscope and a Zeiss fluorescence microscope with an Axioskop digital camera. UV-visible absorption spectra were obtained with a HP 8452A diode array spectrophotometer. The steadystate fluorescence measurements were carried out on a Varian Cary Eclipse fluorescence spectrometer. X-ray diffraction patterns were recorded on a Siemens D500 diffractometer using Ni-filtered Cu K radiation with = Å in 2 scan mode. The molar ratio of the two porphyrins in the porphyrin nanofiber bundles was measured by elemental analysis, UV-visible absorption spectroscopy (Fig. S3) and EDX (Fig. S4). The pink material was first separated from the organic phase by centrifugation or filtration and then rinsed twice with dichloromethane. Elemental analysis calculated for 4 [SbOTPP] + and 1 [H 2 TPPS 4 ] 4- S-1

3 (C 220 H 138 N 20 S 4 O 16 Sb 4 ): C, 67.19; H, 3.54; N, 7.12; O, 6.51; S, 3.26; Sb, Found C, 61.65; H, 3.51; N, 6.51; O, 10.77; S, 3.31; Sb, The Sb:S ratio indicates 3.7 [SbOTPP] + per [H 2 TPPS 4 ] 4-. Self-metallization of the porphyrin nanofiber bundles. Potassium tetrachloroplatinate(ii) (K 2 PtCl 4 ; 99.99%), hydrogen tetrachloroaurate(iii) (HAuCl 4 ; 17 wt.% solution in dilute hydrochloric acid; 99.99%), L-ascorbic acid (99+%), ethylenediamine tetra-acetic acid (EDTA) (99+%), silver nitrate (99.9%), sodium thiosulfate (99+%), and thiourea (99+%) were purchased from Aldrich and used without further purification. Gold(I) sodium thiosulfate (99.9%) was purchased from Alfa Aesar and also used without further purification. All reactant solutions were prepared using ultrapure water. Ascorbic acid is unstable in aerated water, so a stock solution (0.2 M) was freshly prepared before each reaction. K 2 PtCl 4 solution (20 mm) was prepared and equilibrated overnight before use (Ciacchi, L. C.; Pompe, W.; De Vit, A. J. Am. Chem. Soc. 2001, 123, 7371). Gold(I) thiosulfate solution was freshly prepared before use and filtered through a 0.2 m membrane. Silver(I) thiosulfate solution was freshly prepared before use by dropwise addition of 2 ml of silver nitrate solution (0.1 M) to 8 ml of sodium thiosulfate solution (0.1 M). The solution was filtered through a 0.2 micron membrane prior to use. Au(I)-(thiourea) x solution was freshly prepared according to a published procedure (Wang, Z.; Medforth, C. J.; Shelnutt, J. A. J. Am. Chem. Soc. 2004, 126, 16720). Since the porphyrin nanofiber bundles are not easily dispersed in aqueous solutions, they were first immobilized by drying them onto standard holey-carbon coated TEM Cu grids; this also facilitates TEM or SEM imaging. For the photocatalytic metallization reactions, typically 20 L of a suspension of nanofiber bundles in dichloromethane prepared by the synthesis described above was pipetted onto a TEM grid, and the solvent was wicked away using a Kimwipe tissue placed underneath the grid. The TEM grid was submerged in a 2-mL glass vial containing 1 ml of a solution of the metal precursor(s) (typically 0.1 or 1.0 mm) and ascorbic acid or EDTA (typically 20 mm). The vial was placed in a glass water bath (for temperature control), and then the nanofiber bundles on the TEM grid were irradiated with incandescent light (800 nmol cm -2 s -1 ). After light exposure, the TEM grid was rinsed twice with deionized water prior to TEM imaging. Negligible amounts of gold or silver deposition were observed in control experiments without light or the porphyrin nanofiber bundles, confirming that these reactions are predominantly photocatalytic. S-2

4 Supplementary Figure 1 a 10 m b 2 m c 50 m Figure S1. SEM images (a and b) and conventional fluorescence image (c) of porphyrin rods prepared from 105 M [H 2 TPPS 4 ] 4- and 315 M [SbOTPP] + without shaking or stirring the reaction mixture: (a) The rods are up to 1 micron in width and tens of microns in length with a wide size distribution (the background is the holey-carbon film on a TEM grid); (b) at higher magnification the rods are seen to consist of bundles of fibers ~30 nm in diameter; (c) conventional fluorescence image of the porphyrin rods. S-3

5 Supplementary Figure 2 Intensity (arb. u.) a d = 2.1 nm d = 1.0 nm (degree) b 2.2 nm 70 nm Figure S2. (a) Low-angle X-ray diffraction pattern of the porphyrin nanofiber bundles; (b) Highresolution TEM image of a porphyrin nanofiber bundle showing layering along the fiber axis and the minimum inter-lamellar spacing of ~2.2 nm. S-4

6 Supplementary Figure 3 a Absorbance (a. u.) Experimental Simulated b Wavelength (nm) Absorbance (a. u.) Experimental Simulated Wavelength (nm) Figure S3. Simulation of the UV-visible spectrum of the porphyrin nanofiber bundles dissociated in ethanol using the spectra of monomeric [SbOTPP] + or [H 2 TPPS 4 ] 4- in ethanol: (a) Soret-band region, best fit ratio 4.0:1; (b) Q-band region, best fit ratio 3.5:1. S-5

7 Supplementary Figure 4 Counts 4000 C S Sb Cu 3000 Sb 2000 O 1000 Cu Cu Energy (kev) Figure S4. Energy dispersive X-ray spectrometry (EDX) of the porphyrin nanofiber bundles. Signals from Cu are due to the copper TEM grid. The atomic ratio of Sb:S was found to be 56.1:43.9, based on the L line of Sb and the K line of S, and averaged over the six different measured areas. This atomic ratio corresponds to a ratio of 5.1:1.0 for [SbOTPP] + /[H 2 TPPS 4 ] 4-. Given that EDX is typically less sensitive to light elements such as sulfur, this ratio is close to the value of 4:1 expected for an ionic solid composed entirely of porphyrins. S-6

8 Supplementary Figure M [SbOTPP] + in dichloromethane 10.5 M [H 2 TPPS 4 ] 4- in water Absorbance [H 2 TPPS 4 ] 4- x Wavelength (nm) Figure S5. UV-visible spectra of monomeric [SbOTPP] + and [H 2 TPPS 4 ] 4- solutions. The spectra were measured using a 1-mm quartz cuvette, except for the expansion of the Q-band region of [H 2 TPPS 4 ] 4- which was measured using a 1-cm cuvette. S-7

9 Supplementary Figure Intensity (a. u.) Wavelength (nm) Figure S6. Emission spectra of monomeric solutions of [SbOTPP] + in dichloromethane (black curve) and [H 2 TPPS 4 ] 4- in water (red curve) obtained with 420-nm excitation. S-8

10 Supplementary Figure 7 a 100 nm b 100 nm Figure S7. TEM images of platinized porphyrin nanofiber bundles showing various degrees of coverage with platinum dendrites: (a) dense, but non-continuous; (b) virtually continuous. The platinization was achieved by 6 minutes of light exposure in the presence of 20 mm ascorbic acid and 0.1 mm K 2 PtCl 4 (a) or 1.0 mm K 2 PtCl 4 (b). S-9

11 Supplementary Figure 8 70 nm Figure S8. TEM image of porphyrin nanofiber bundles gilded by 8 minutes of light exposure in the presence of 0.1 mm Au(I)-thiosulfate complex and 20 mm ascorbic acid. S-10

12 Supplementary Figure 9 70 nm Figure S9. TEM image of porphyrin nanofiber bundles decorated with flattened silver nanoparticles. The silver metallization was achieved by 8 minutes of light exposure in the presence of 1.0 mm Ag(I)-thiosulfate complex and 20 mm ascorbic acid. S-11

13 Supplementary Figure nm Figure S10. TEM image of porphyrin nanofiber bundles prepared from [SbOTPP] + and [CuTPPS 4 ] 4- and platinized by 6 minutes of light exposure in the presence of 0.1 mm K 2 PtCl 4 and 20 mm ascorbic acid. S-12