Vibrational Spectra of Thiolate-Protected Gold Nanocluster with Infrared Reflection Absorption Spectroscopy: Size- and Temperature-Dependent Ordering Behavior of Organic Monolayer

Abstract

Vibrational spectra of thiolate-protected gold nanoclusters, prepared in a monolayer manner using the Langmuir–Blodgett method, were measured by means of infrared reflection absorption spectroscopy (IRAS). A transferred monolayer of gold nanoclusters ligated by dodecanethiolate or 2-phenylethane-1-thiolate onto a single-crystal gold (Au) surface of Au(111) exhibits worthy IRAS spectra that reveal temperature-dependent behaviors from 100 to 340 K as well as comprehensive peak assignments based on density functional theory calculations: the conformation change in ligands between all trans and gauche defect forms with temperature. In addition to the temperature dependence, the cluster size dependence of alkyl and phenyl moieties is discussed, compared with the IRAS spectra of the corresponding self-assembled monolayers (SAMs) on Au(111). Ligands spreading three-dimensionally from the Au core determine the coordination structure of the ligated Au nanoclusters.

Tailoring the Electron–Phonon Interaction in Au25(SR)18 Nanoclusters via Ligand Engineering and Insight into Luminescence

“…To simplify the problem, we neglect the effect of CC, C–C, and C–H vibrations from the carbon tail and treat the carbon tail as a whole when we discuss their effect. It is reasonable because the vibrations of light atoms (i.e., C, H) are far beyond the frequency region that we are interested in . Therefore, the possible origin of optical phonons can be narrowed down to the Au­(inner core)–(SR)–Au­(motif)–(SR)–Au­(motif)–(SR)–Au­(inner core) chain.…”

“…It is reasonable because the vibrations of light atoms (i.e., C, H) are far beyond the frequency region that we are interested in. 58 Therefore, the possible origin of optical phonons can be narrowed down to the Au(inner core)−(SR)−Au(motif)− (SR)−Au(motif)−(SR)−Au(inner core) chain. The observed 330 cm −1 optical phonon mode in Au 25 (BM) 18 − and 390 cm −1 optical phonon mode in Au 25 (PET) 18 − are close to the Au−S vibration modes in the Au 2 (SR) 3 motifs measured by Raman spectroscopy.…”

Reflection Absorption Infrared Spectroscopy Characterization of SAM Formation from 8-Mercapto-N-(phenethyl)octanamide Thiols with Phe Ring and Amide Groups

“…At initial adsorption time (5 s), the intense band near 2926 cm −1 , due to asymmetric stretching vibration of CH 2 groups (d − ), dominates in the spectrum. The symmetric stretching vibration of methylene groups is visible near 2858 cm −1 (d + ), while two bands at 3033 and 3067 cm −1 are associated with stretching vibration ν(=C-H) and demonstrate the presence of the terminal Phe ring at the interface [39]. The high frequency value of ν as (CH 2 ) and ν s (CH 2 ) modes indicates the disordered state of the alkyl chains at the interface [12,15,48].…”

“…Figure 2 compares infrared absorption spectra of bulk MOPHE and MOPHE-D 5 compounds dispersed in the KBr tablet. Assignments of the main infrared bands based on our calculations and previous publications [30][31][32][33][34][35][36][37][38][39] are given in Table 1. Figure 2 compares infrared absorption spectra of bulk MOPHE and MOPHE-D5 compounds dispersed in the KBr tablet.…”

Deposition of Extended Ordered Ultrathin Films of Au38(SC2H4Ph)24 Nanocluster using Langmuir–Blodgett Technique

“…[ 18 ] Nevertheless, the interactions between neighboring particles tend to be relatively weak for particles in the size range of 1–2 nm, which explains why only a few examples of LB films based on gold nanoclusters have been reported. [ 34–37 ]…”