Alkyl-Modified Gold Surfaces: Characterization of the Au–C Bond

Abstract

The surface of gold can be modified with alkyl groups through a radical crossover reaction involving alkyliodides or bromides in the presence of a sterically hindered diazonium salt. In this paper, we characterize the Au-C(alkyl) bond by surface-enhanced Raman spectroscopy (SERS); the corresponding peak appears at 387 cm close to the value obtained by theoretical modeling. The Au-C(alkyl) bond energy is also calculated, it reaches -36.9 kcal mol similar to that of an Au-S-alkyl bond but also of an Au-C(aryl) bond. In agreement with the similar energies of Au-C(alkyl) and Au-S-(alkyl), we demonstrate experimentally that these groups can be exchanged on the surface of gold.

A theoretical and experimental study of the adsorptive removal of hexavalent chromium ions using graphene oxide as an adsorbent

“…The highest adsorption energy is obtained for the Pose_3, in which the dichromate ion (where its oxygen atom bonded between two Cr atoms) is located near the surface hydroxyl group of the GO. To correctly assess the interaction type [14,22,23] between the chromate ions and GO surface, the NCI plot and the reduced density gradient (RDG) vs. sign(λ)ρ were computed [31] for the highest adsorption site, in this case, Pose_3. The visualization of the NCI surface (Figure 4(a)) and the RDG vs sign(λ)ρ (Figure 4(b)) supports that the adsorption interaction is a van der Waals one.…”

“…Selfconsistent-field (SCF) convergence criterion was set to the root-mean-square change in the electronic density to be less than 10 −6 eV. All energy minima were characterized by performing a vibrational analysis to ensure the lack of imaginary frequencies [22,23]. The adsorption energy [14,18,23] was calculated as follows:…”

Interactions between the Aryldiazonium Cations and Graphene Oxide: A DFT Study

“…Although the adsorption of the diazonium salts onto the metal surface is evidenced experimentally from corrosion measurements in the case of iron [3], the interaction energies, adsorption geometry, and the interaction type between the GOx surface and the aryldiazonium cations remain up to now unknown for the GOx surface. For the gold surface, the calculated bond dissociation energy (BDE) of the grafted aryl or alkyl moiety is ≈40 kcal/mol [6,12]. e adsorption of the diazonium cation is the first step for the grafting reaction.…”

“…e calculations in water were performed using COnductor-like Screening MOdel (COSMO) [21]. e adsorption energy, both in vacuum and water models, is evaluated as follows [6,13,20]:…”

“…[2] represents the most straight forward strategy to achieve surface modification of materials regardless of their chemical composition nor their conductivity, a feature that is lacking in the case of other molecules (i.e., although thiols offer an elegant way to achieve modification of noble metals, they are not applicable for surface modification of polymers (similar case stand for phosphonic or silanes which are applicable only in the case for surfaces that contain oxyhydroxy groups)) [3]. To date, the grafted layers derived through electrochemical [1,[3][4][5][6], sonochemical [7], or thermal dediazonation reactions have been characterized by a vast number of analytical methods (RBS, Tof-SIMS, XPS, IRRAS, AFM, TGA, etc.) [3].…”