Influence of the metal electronic properties on the sum-frequency generation spectra of dodecanethiol self-assembled monolayers on Pt (111), Ag (111) and Au (111) single crystals

Self-assembled organic monolayers on gold nanoparticles: A study by sum-frequency generation combined with UV–vis spectroscopy

“…5, we clearly see three vibration modes, interfering destructively with a rather constant SFG background coming from the AuNPs substrate. In keeping with previous SFG works on similar organic 1-dodecanethiol SAMs adsorbed on thick films or Au(1 1 1) single crystals [11], these vibration modes located at 2881, 2941 and 2968 cm −1 are related to the symmetric, Fermi resonance and degenerate stretching modes of the methyl CH 3 end-groups, respectively. Moreover, this spectrum exhibits two weaker vibration modes at ∼2850 and ∼2915 cm −1 related to the methylene CH 2 alkane chains symmetric and asymmetric stretching modes.…”

“…In previous works [11,14], it was experimentally shown that the s-d interband electronic properties of Au(1 1 1) single crystals or thick Au(1 1 1) films was the physical process accounting for the interference patterns observed in SFG experiments and analogous to the spectra in Figs. 5 and 6.…”

“…(1) shows why the interfacial SFG response exhibits a strong interference pattern between the non-linear activities of the AuNPs and the 1-dodecanethiol molecules, as illustrated in Tables 1 and 2 by the important phase shift (Φ − ϕ > 2.5 rad). Even if the interband activity of the second order non-resonant susceptibility of AuNPs is not involved in the enhancement of the SFG signal at the interface due to its weak amplitude (A ≤ a q ), this is the physical origin of the interference pattern [11,14].…”

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

“…2B, the enhancement of the SFG response at 550 nm visible wavelength is explained by the evolution of jw ð2Þ NR j 2 . Indeed, it is related to an interband s-d electronic transition of Au that resonates when the corresponding SFG photon wavelength is 480 nm (2.58 eV) [10]. No similar enhancement is observed on Ag (1 1 1) given that the SFG wavelength range required (315 nm, 3.93 eV) is not accessible here (Fig.…”

“…1A-C. We have simulated the metal non-linear contribution jw ð2Þ NR j 2 using Eq. (3) and the metal non-linear susceptibility parameters (jw ð2Þ NR j, F), reported in a previous work [10]. jw ð2Þ NR j 2 is compared to A Fresnel in Fig.…”