Electronic Supplementary Information Raman and computational study of solvation and chemisorption of thiazole in silver hydrosol Maurizio Muniz-Miranda, *a Marco Pagliai, a Francesco Muniz-Miranda b and Vincenzo Schettino a,b Experimental Details Following the procedure proposed by Creighton et al. 1 the Ag hydrosols have been prepared by adding AgNO 3 (99.9999% purity, Aldrich) to excess NaBH 4 (99.9% purity, Aldrich). The ligand adsorption was obtained by adding thiazole (99% pu- rity, Aldrich) to silver colloids in 10 −3 M concentration. NaCl (99.998% purity, Aldrich) was added to Ag colloids in 10 −3 M concentration to improve the SERS enhancement. Raman spectra of thiazole as pure liquid, in CCl 4 , in H 2 O, in D 2 O, in solution and in Ag hydrosol were recorded using the 514.5 nm line of a Coherent argon ion laser, a Jobin-Yvon HG2S monochromator equipped with a cooled RCA-C31034A photomultiplier, and a data acquisition facility. In the 400 − 1500 cm −1 region the Raman spectrum of liquid thiazole closely corresponds, regarding frequencies and relative intensities, to that in CCl 4 solution. To impair the thermal effects due to the laser light, a defocused beam with low power (20 mW) was used. Power density measurements were performed with a power meter instrument (model 362; Scientech, Boulder, CO) giving ∼5% accuracy in the 300-1000 nm spectral range. Computational Details Car-Parrinello molecular dynamics simulation Ab initio molecular dynamics simulation have been performed with the CPMD package 2 on a system made up of 64 heavy water and 1 thiazole molecules in the NVE ensemble. The sam- ple has been simulated in a cubic box of edge length 12.6983 ˚ A, with periodic boundary conditions. BLYP exchange and correlation functional 3,4 has been adopted, along with norm- conserving Martins-Troullier pseudopotentials 5 and Kleinman- Bylander decomposition. 6 Plane wave expansions have been truncated at 85 Ry while a 600 atomic units (a.u.) electronic a Dipartimento di Chimica “Ugo Schiff”, via della Lastruccia 3, Sesto Fiorentino (FI), Italy. Fax: +390554573077; Tel: +390554573091; E-mail: muniz@unifi.it b European Laboratory for Non-Linear Spectroscopy (LENS), via Nello Carrara 1, Sesto Fiorentino (FI), Italy. fictitious mass has been set. The system has been simulated for about 26 ps with a time step of 4 a.u. (∼ 0.096 fs). The average temperature was 302 ± 16 K. Wavelet transform Fourier Transform is usually employed to extract the frequency content from a time-dependent signal, without a simultaneous localization in both frequency and time domain. In order to obtain vibrational properties from molecular dynamics trajec- tories, Fourier Trasforms are performed, 7–9 but it has been re- cently shown 10–12 that similar results can be obtained with a wavelet analysis 13 approach. Given an input function f (t), its wavelet transform, W n (s), is defined as W n (s)= ∫ +∞ −∞ dt ′ f (t ′ )ψ ∗ ( t ′ − n s ) , (1) whose discretized expression is W n (s)= N−1 ∑ n ′ =0 f (n ′ · δt)ψ ∗ ( (n ′ − n) · δt s ) . (2) In the two previous equations, following the formalism of Tor- rence and Compo, 14 , the ψ function is called “mother wavelet” and is stretched and translated in time by the two parameters s and n, respectively. n ′ is the time-step index, δt is the time step, s is the wavelet scale. The algorithm adopted for the present paper computed the wavelet transform in the Fourier space as: W n (s)= N−1 ∑ k=0 ˆ f k · ˆ ψ ∗ (sω k )e iω k nδt , (3) where k is the frequency index, ω k is the angular frequency and ˆ f k and ˆ ψ are the Fourier transforms of the time series f n and of the mother wavelet ψ adopted, respectively. The mother wavelet used in this work is given by the Morlet function, since Kirby 15 proved it best reproduces the Fourier power spectrum: ψ(t)= π −1/4 e iω 0 t−t 2 /2σ 2 . (4) 1 Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2011