Self-Assembled Monolayers of Nitrile-Functionalized Alkanethiols on Gold and Silver Substrates

Abstract

Self-assembled monolayers (SAMs) formed from nitrile-functionalized alkanethiols (AT), NC(CH 2 ) 16 SH (NC-C16), on (111) gold and silver substrates were characterized by X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and contact angle measurements. The average chain tilt angles in NC-C16/Ag and NC-C16/Au were estimated to be 29.5°( 5°and 42.5°( 5°from the surface normal, respectively, while the data suggest lower ordering for NC-C16/Au. The -CtN bonds were found to be predominantly oriented in the surface plane with a tilt angle of 65°( 7°for both NC-C16/Au and NC-C16/ Ag. Comparison with previous data on CH 3 -terminated SAMs reveals that substitution of weakly interacting CH 3 groups by the CN entities results in an increase in the average tilt angles of the alkyl chains by ∼7.5°a nd ∼17.5°in AT/Au and AT/Ag, respectively. A strong electrostatic interaction between the polar nitrile groups is assumed to underlie the structural behavior by controlling a balance between the headgroupsubstrate and interchain interactions. The near-parallel orientation of the nitrile groups to the surface in both of these SAMs can be explained on the basis of minimization of the unfavorable CN-CN dipole-dipole interactions.

Electronically induced modification of thin layers on surfaces

“…These site-specific signals which are due to direct photon induced bond breaking do not depend on temperature as expected. However, they are smaller than other desorption maxima even at 50 K. This indicates that the major part of the desorption signal from such layers is due to unspecific, not site selective excitations by secondary electrons, even for site selective primary excitations of states with large cross section such as the [N1s]p* resonance [16].…”

Dipodal Ferrocene‐Based Adsorbate Molecules for Self‐Assembled Monolayers on Gold

“…In XPS, only a single N 1s emission related to the isocyanide nitrogen appears at 399.9 eV, [54] indicating an exclusive isocyanide-mediated bidentate bonding of 1 to the Au substrate with no contributions from monodentate binding or physisorption. This interpretation is strongly supported by IRRAS data, which also suggest an essentially vertical orientation of the adsorbate molecules on the gold surface.…”

A New Approach for the Fabrication of Strongly Heterogeneous Mixed Self‐Assembled Monolayers

“…This observation suggests the , FBPET/DMF for 2 h). These Fe 2p 3/2 XPS data show the characteristic emission related to the iron atom in the ferrocene moiety of FBPET, [4] as seen from the comparison with the corresponding spectrum of FBPET/Au (Figure 4 b). Taking FBPET/Au as the reference, we could estimate the FBPET content in the mixed DDT-FBPET film to be approximately 20 %.…”

“…[3] The assembly of the molecules can, however, exhibit low structural quality, owing to the distorted balance of the structure-building forces in the SAM, which generally stems from the presence of bulky or strongly interacting active groups. [4] In addition, the performance of these groups can suffer from their mutual interaction (if they are not separated to the necessary extent) and from interaction with the substrate (if the angle between the molecules and the substrate is small). One can, however, avoid these problems by implanting the device molecules into a passive molecular matrix, that is, by preparing heterogeneous mixed SAMs.…”