1. 1 Preparation and characterization of electrodeposited gold SERS substrates Pierre Brodard, J. Elias, L. Philippe and J. Michler ICES 2012 | Porquerolles | 04.10.2012

2. Gold flails on transparent conductive oxide 2 SYNTHESIS SEM images (20 min. deposition) J. Elias, P. Brodard, M. G. C. Vernooij, J. Michler, L. Philippe, Electrochim. Acta 2011 (56) 1485. substrate: glass/SnO 2 :F bath: KAu(CN) 2, pH 7.3, 55°C gelatin: 2 wt% electrodeposition performed at constant potential: - 0.8 V deposition time varied: 2.5 - 50 min 3-electrodes electrochemical cell: working electrode: TCO counter electrode: Pt spiral wire reference electrode: Ag/AgCl

3. Gold flails on transparent conductive oxide 3 CHARACTERIZATION EDX => preferential orientation (perpendicular to {111} planes) => no other phases or impurities => only Au (structures dispersed on Cu grid) 111 XRD J. Elias, P. Brodard, M. G. C. Vernooij, J. Michler, L. Philippe, Electrochim. Acta 2011 (56) 1485.

4. Gold flails on transparent conductive oxide 4 CHARACTERIZATION secondary e - image FIB-cut flail EBSD J. Elias, P. Brodard, M. G. C. Vernooij, J. Michler, L. Philippe, Electrochim. Acta 2011 (56) 1485. 1.many Au nuclei formed instantaneously: Au(CN) 2 − + e − → Au + 2CN − => gold nanoelectrodes 2.gelatin + adsorb onto gold surface => slow growth rate 3.face-selective adsorption of gelatin => {111} facets

5. Gold flails on transparent conductive oxide 5 RESULTS SEM images J. Elias, P. Brodard, M. G. C. Vernooij, J. Michler, L. Philippe, Electrochim. Acta 2011 (56) 1485.

6. Gold flails on transparent conductive oxide 6 p-mercaptoaniline (pMA = 4-aminobenzenethiol) monolayer (100  M pMA, 3 h, rinsing EtOH) SERS 632.8 nm, 1-2 mW, laser spot ∼ 1  m, 30 s cluster of flails  massive SERS single flail  no SERS J. Elias, P. Brodard, M. G. C. Vernooij, J. Michler, L. Philippe, Electrochim. Acta 2011 (56) 1485.

7. Gold flails on transparent conductive oxide 7  SERS effect localized in hot-spots (= contact points) SERS SERS effect increases with number of flails ! (tested with pMA and BCB, plateau from about 5 flails, not shown) J. Elias, P. Brodard, M. G. C. Vernooij, J. Michler, L. Philippe, Electrochim. Acta 2011 (56) 1485.

8. Gold flails on transparent conductive oxide 8 SERS If SERS = contact points, why SERS decreases with size of flails ?  spikes = NANOSPACERS J. Elias, P. Brodard, M. G. C. Vernooij, J. Michler, L. Philippe, Electrochim. Acta 2011 (56) 1485.

9. Gold thin films with different morphologies 9 J. Elias, M. Gisowska, P. Brodard, R. Widmer, Y. de Hazan, T. Graule, J. Michler, L. Philippe, Nanotechnology 2012 (23) 255705. substrate: glass/SnO 2 :F bath: KAu(CN) 2 + KH 2 PO 4, 55°C electrodeposition performed in potential range: - 0.7 V to -1.2 V stirred at 300 rpm during electrodeposition 3-electrodes electrochemical cell: working electrode: TCO counter electrode: Pt spiral wire reference electrode: Ag/AgCl SYNTHESIS -0.7 V -0.8 V -0.9 V -1.0 V -1.1 V -1.2 V => flakes

10. Gold thin films with different morphologies 10 J. Elias, M. Gisowska, P. Brodard, R. Widmer, Y. de Hazan, T. Graule, J. Michler, L. Philippe, Nanotechnology 2012 (23) 255705. MECHANISM direct charge transfer reaction hydrogen evolution reaction = inhibition of growth time evolution:

11. Gold thin films with different morphologies 11 J. Elias, M. Gisowska, P. Brodard, R. Widmer, Y. de Hazan, T. Graule, J. Michler, L. Philippe, Nanotechnology 2012 (23) 255705. RESULTS AFM RMS: roughness -0.7 V -0.8 V -0.9 V -1.0 V -1.1 V -1.2 V

12. Brilliant Cresyl Blue (BCB = C 17 H 20 N 3 OCl ∙ ½ ZnCl 2 ) drop-coated (10 -7 M BCB in EtOH) Gold thin films with different morphologies 12 J. Elias, M. Gisowska, P. Brodard, R. Widmer, Y. de Hazan, T. Graule, J. Michler, L. Philippe, Nanotechnology 2012 (23) 255705. SERS 632.8 nm, 0.25-0.50 mW, laser spot ∼ 1  m, 0.1 s

13. Gold thin films with different morphologies 13 J. Elias, M. Gisowska, P. Brodard, R. Widmer, Y. de Hazan, T. Graule, J. Michler, L. Philippe, Nanotechnology 2012 (23) 255705. SERS evolution of SERS effect: competition between - generation of hot-spots (roughness) - size of nanostructures (voltage)

14. Conclusion 14  SERS in contact points  no SERS on single spikes  gap size control by spike size  SERS proportional to roughness  SERS inversely proportional to flakes size  optimum in SERS effect for one surface