Supplementary information

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1 Supplementary information doi: /nchem.1025 Platinum nanocrystals selectively shaped using facet-specific peptide sequences Chin-Yi Chiu 1, Yujing Li 1, Lingyan Ruan 1, Xingchen Ye 2, Christopher B. Murray 2,3 & Yu Huang 1,4 * 1 Department of Materials Science and Engineering, 4 California NanoSystems Institute, University of California, Los Angeles, California 90095, USA. 2 Department of Chemistry, 3 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. Supplementary Information 1. Figure S1 SEM and TEM images of starting substrates for peptide selection. 2. Figure S2 Liquid chromatography (LC) and mass spectrum of T7 and S7 peptide sequences. 3. Figure S3 TEM images of NCs from T7- and S7- controlled reactions in the case of K 2 Pt(II)Cl 4 precursor 4. Figure S4 Schematic model of cube projection shades. 5. Figure S5 HRTEM images of truncated cubes. 6. Figure S6 HRTEM images of incomplete cubes. 7. Figure S7 Schematic model of tetrahedron projection shades with the observed TEM shapes. 8. Figure S8 HRTEM images of Pt tetrahedron tilting. 9. Figure S9 TEM images of NCs as a function of peptide concentration. 10. Estimation of T7-Pt{100} and S7-Pt{111} binding constants. 11. Figure S10 Preliminary peptide configuration simulation and binding on Pt surface. nature chemistry 1 1

2 1. SEM and TEM images of starting substrates for peptide selection. Figure S1 Starting substrates for peptide selection. SEM images of Pt octahedrons (a) and Pt cubes (d) on Si substrates, respectively. b and c show TEM and HRTEM images of assynthesized Pt octahedrons, respectively. e and f show TEM and HRTEM images of assynthesized Pt cubes, respectively. 2. Liquid chromatography (LC) and mass spectrum of T7 and S7 peptide sequences. Figure S2 Liquid chromatography (LC) of the T7 peptide (a) and its corresponding mass spectrum of the samples eluted at about 21.5 min (b). Liquid chromatography (LC) of the S7 2 peptide (c) and its corresponding mass spectrum of the samples eluted at about 19.5 min (d). 3. TEM images of NCs from T7- and S7- controlled reactions in the case of nature chemistry 2

3 peptide (c) and its corresponding mass spectrum of the samples eluted at about 19.5 min (d). 3. TEM images of NCs from T7- and S7- controlled reactions in the case of K 2 Pt(II)Cl 4 precursor. Figure S3 a, TEM image of the obtained NCs from T7- control reaction (1 mm of K 2 PtCl 4, 10 g/ml of T7; 1 mm of ascorbic acid; 0.8 mm of NaBH 4 ); HRTEM of a Pt cube with a zone axis [100] (inset). b, TEM image of the obtained NCs from S7- control reaction (1 mm of K 2 PtCl 4, 30 g/ml of S7; 0.5 mm of ascorbic acid; 0.8 mm of NaBH 4 ); HRTEM of a Pt tetrahedron with a zone axis [110] (inset). c, blank controlled reaction (1 mm of K 2 PtCl 4, 0.5 mm of ascorbic acid; 0.8 mm of NaBH 4 ). The synthetic method is the same as described in the Methods and the concentrations addressed here are final concentration with a final solution volume, 5 ml. 4. Schematic model of cube projection shades. Figure S4 Schematic model of the corresponding projections of cubes and truncated cubes projected along [001]. 3 nature chemistry 3

4 5. HRTEM images of truncated cubes. Figure S5 HRTEM images of truncated cubes showing the truncated facets {111} and {110}, respectively. a, HRTEM image of the truncated cube and its corresponding FT pattern in (b), indicating it was recorded along [001] zone axis and predominated enclosed by {100}. After tilting angle, in HRTEM image (c) the lattice fringe was confirmed with the spacing of 0.23 nm, indicating the truncated facet is {111}. d, HRTEM image of the truncated cube and the selected area was zoomed in and shown in (e); the spacing of the lattice fringe is 0.14 nm corresponding to {110} confirmed by the FT pattern shown in (f), indicating the truncated facet is {110}. 6. HRTEM images of incomplete cubes. Figure S6 HRTEM images of incomplete cubes obtained from the T7 control reaction. a, TEM image of the Pt cubes controlled by T7 peptide. b-d, HRTEM images of truncated cubes and their corresponding FT patterns, indicating these non-cubic like NCs are incomplete cubes predominated enclosed by {100}. The effect of Pt-{100} binding peptide sequence, T7, on stabilizing {100} facets was further confirmed. 4 nature chemistry 4

5 7. Schematic model of different projection shades of tetrahedron with the observed TEM images. Figure S7 Schematic model of tetrahedron projected along different directions and their corresponding HRTEM images, confirming the varied shapes of the NCs observed in TEM image are tetrahedron projections. 8. HRTEM images of Pt tetrahedron tilting. Figure S8 HRTEM images of a single Pt tetrahedron recorded with different angles. 25 (a); 20 (b); 10 (c); 5 (d); 0 (e). f-j show the corresponding FT patterns of (a-e) confirming the tetrahedron is predominantly enclosed by {111} facets. The images were recorded by tilting zone axis between [112] to [110]. 5 nature chemistry 5

6 9. TEM images of NCs as a function of peptide concentration. Figure S9 TEM images of NCs as a function of T7 and S7 peptide concentration, respectively. 5 l/ml of T7 (a); 10 l/ml of T7 (b); 30 l/ml of T7 (c); 50 l/ml of T7 (d). e, Pt cubes population as a function of T7 peptide. 5 l/ml of S7 (f); 10 l/ml of S7 (g); 30 l/ml of S7 (h); 50 l/ml of S7 (i). j, Pt tetrahedrons population as a function of S7 peptide. Except for peptide concentration, the synthetic condition for the same peptide sequence controlled reaction is the same. Scale bars: 20 nm. 10. Estimation of T7-Pt{100} and S7-Pt{111} binding constants. According to the study conducted by Sarikaya s group about the adsorption kinetics of gold-binding peptide on to gold substrate 1, the steady-state fractional coverage of the gold surface by peptides is given by C ( ) = 1 C+ K eq where is the fraction of surface covered, C is the peptide concentration, and K eq is the equilibrium binding constant. Based on this formula, assume close to monolayer absorption of peptides ( =0.99) at C = 1.2 x10-5 M (10 g/ml) for T7(MW:804) and at C = 3.7 x10-5 M (30 g/ml) for S7(MW: 817), we can derive the binding constants for T7- Pt-{100} to be 8.3 x10 6 M -1 and that of the S7-Pt-{111} is 2.7 x10 6 M -1 similar to the reported value 3.4 x 10 x10 6 M nature chemistry 6

7 11. Preliminary peptide configuration simulation and binding on Pt surface Figure S10 Preliminary binding studies. (a, c) Schematics of S7 and T7 binding on Pt-{111} and Pt-{100} surface, respectively. (b, d) Top view of functional groups binding on Pt-{111} and Pt- {100}, respectively. The yellow shapes indicate possible binding configurations corresponding to the functional groups. Grey spheres indicate C atoms, white spheres indicate H, red spheres indicate O atoms and blue spheres indicate N atoms. The peptide configurations were obtained by constructing initial primary structures in HyperChem Professional (Ver. 8.0) and then docking the structure into Accelrys Materials Studio (MS) Modeling toolkit (Ver. 4.0). The energy minimization was performed with Discover module in MS software. After energy minimization in vacuum, S7 sequence shows a heavily coiled structure, with aromatic group (on Phenylalanine, F) at the periphery of the molecule. We speculate the F may contribute to the specific binding on {111} facet, as suggested in a previous work by Naik et al. 3 that amino acids containing aromatic groups prefer to bind to {111} facets due to the hexagonal spacing of 1.6 Å between available lattice sites on the {111} surfaces (Fig.S10 a-b). The T7 sequence is elongated in axial direction and peripheralized with oxygen and nitrogen atoms especially at the TLT end. The highly hydroxylated TLT end makes it possible for oxygen atoms to approach adjacent Pt atoms on {100} facets, as shown in Fig.S10 (c,d). 4 The four oxygen atoms in Fig. S10(d) represent their positions on the TLT end of T7 peptide. According to their relative positions, we can fit three of the oxygen (O) atoms (designated as A, B, and C) to the bridge sites between two adjacent Pt atoms while fit the fourth O (designated as D) on top of a Pt atom. The arrangement of the O atoms has a fair consistency with the possible binding sites configuration on Pt-{100} shown in yellow in Fig. S10(d). We suggest a slight reconstruction may occur in solution and upon binding to metal surface, to make the D atom fall into the neighbouring bridge site, which makes the energy even lower. 5 In addition, the stabilized configuration shows that the peptide can stand on the surface, making it possible for the T7 peptide to form monolayer and stabilize the {100} surface. nature chemistry 7

8 References: 1. Tamerler, C. et al. Materials specificity and directed assembly of a gold-binding peptide. Small 2, (2006). 2. Seker, U.O.S. et al. Adsorption behavior of linear and cyclic genetically engineered platinum binding peptides. Langmuir 23 (15), (2007). 3. Heinz, H. et al. Nature of molecular interactions of peptides with gold, palladium, and Pd-Au bimetal surfaces in aqueous solution. J. Am. Chem. Soc. 131, (2009). 4, Oren, E.E., Tamerler, C. & Sarikaya, M. Metal recognition of septapeptides via polypod molecular architecture. Nano Lett. 5, (2005). 5. Karlberg, G. S., Adsorption trends for water, hydroxyl, oxygen, and hydrogen on transition-metal and platinum-skin surfaces. Physical Review B 74 (15) (2006). 8 nature chemistry 8