Sum frequency generation (SFG) study of the pH-dependent water structure on a fused quartz surface modified by an octadecyltrichlorosilane (OTS) monolayer

Probing the Molecular Conformation of Self-Assembled Monolayers at Metal/Semiconductor Interfaces by Vibrational Sum Frequency Generation Spectroscopy

“…A picosecond Nd:YAG laser (PL2143B, Ekspla) was used to pump an optical parametric generation/ optical parametric amplification/difference frequency generation (OPG/OPA/DFG) system to produce tunable infrared radiation (2.3-8.5 µm). 14,15,25 The second harmonic output of the YAG (yttrium-aluminum-garnet) laser at 532 nm was used as the visible light source. At the incident angle of 70°for visible and of 50°for infrared light, two beams were loosely focused onto the sample.…”

“…1 SFG spectroscopy has also been adapted to the study of molecular conformations of self-assembled monolayers (SAMs) formed on various substrates. [7][8][9][10][11][12][13][14][15][16] Two decades ago, GuyotSinnest et al reported that octadecyltrichlorosilane (OTS) monolayers on silica are oriented normal to the surface. 8 Hines et al have shown that alkanethiolate SAMs on gold and silver are relatively more ordered than those prepared on platinum; however, the latter can be "straightened" by applying electrochemical potentials.…”

Interference effects in the sum frequency generation spectra of thin organic films. II: Applications to different thin-film systems

“…2͑a͒, the spectra at n = 70 and 80 mainly show two weak dips around 2878 and 2944 cm −1 , resembling those at n = 4. Note that the symmetric ͑d + ͒ and asymmetric ͑d − ͒ C-H stretching modes of the methylene ͑CH 2 ͒ groups, arising from the gauche defects in the layers, [14][15][16][17] can also be observed around 2850 and 2920 cm −1 , respectively. These film defects sometimes appear in the LB multilayers during film deposition and their extent is not experimentally controllable.…”

Photocatalytic oxidation of the organic monolayers on TiO2 surface investigated by in-situ sum frequency generation spectroscopy

“…On the other hand, in the case of OTS monolayer, hydrolyzed OTS molecules are anchored not only on the TiO 2 surface with the Si-O bond but also bind to each other by the Si-O-Si network through the silane coupling reaction. 32,33 The strong chemical interaction in the OTS monolayer restricts the lateral mobility of the individual OTS molecule in the monolayer. When some of the OTS molecules in the SAM were oxidized, the remaining OTS molecules could not repair the oxidized sites (Scheme 1(b)) in order to reconstruct ordered domains by a surface diffusion process as that happen on the AA monolayer.…”

“…30,31 A SAM of octadecyltrichlorosilane (OTS) was prepared on the TiO 2 surface following the procedures described elsewhere. [32][33][34][35][36] A broad-band SFG system was used to characterize the structure and conformational ordering of the two monolayers. Details about the system were described elsewhere.…”