Mixed Self‐Assembled Monolayers with Internal Urea Group on Silica Surface

Abstract

In this study, we report the successful grafting on silica surfaces by the coadsorption method, of mixed nitrobenzyl ester‐/methyl‐terminated self‐assembled monolayers (SAMs), with ratios of two coupling agents (30/70) and (10/90). We show that the preparation of mixed monolayers using two organosilanes with internal urea groups in the alkyl chain seems to be appropriate to obtain a monolayer composition similar to the molar ratio of the two silanes in the deposition solution. This behavior could be due to the presence of the polar urea groups in the molecular structure of both organosilanes which allows them to have the same ability of self‐assembly by hydrogen‐bonding and also the same affinity with the hydrophilic surface. To locate the ester functions at the surface of the mixed monolayers, we investigated the covalent immobilization of amino functionalized gold nanoparticles (GNPs) as nanoscale marker. Polarization modulation infrared reflection‐adsorption spectroscopy (PM‐IRRAS) and atomic force microscopy (AFM) were used to monitor the chemical modifications of the silica surfaces and to demonstrate the successful attachment of gold nanoparticles onto the modified surfaces. Finally, we show that the mixed SAMs were grafted with a phase separation.

Self-assembly of amino-terminated monolayers depending on the chemical structure

“…PM-IRRAS experiments were performed using a FTIR spectrometer equipped with a PM-IRRAS optical bench, 50 following the experimental procedure previously published. 49 The PM-IRRAS spectra were recorded at a 4 cm −1 spectral resolution during the 4 h acquisition time. The PM-IRRAS spectra were calibrated in order to be presented in IRRAS units ( i.e.…”

“…The silylated coupling agents bearing urea or carbamate groups were used to provide functionalized hydrogen-bonding SAMs. 46–49…”

“…The silylated coupling agents bearing urea or carbamate groups were used to provide functionalized hydrogenbonding SAMs. [46][47][48][49] We investigated the influence of the organosilane structure and the method of preparation on the amino-terminated monolayer organization. The reactivity of the terminal amine was evaluated by using a coupling reaction with a fluorescent probe.…”

Enhancing the Sensitivity of Biotinylated Surfaces by Tailoring the Design of the Mixed Self-Assembled Monolayer Synthesis

“…The literature on amide-based hydrogen bonds within SAMs is rather limited 32 − 35 despite the fact that it has been proven that SAMs bearing amide moieties lead to more robust and stable surfaces suitable for further modification and biofunctionalization. 34 This work provides further compelling evidence of the validity of such an approach with the support of several characterization tools. As a proof of concept, biotin was selected as the biorecognition element and streptavidin (SA) as the target analyte as the biotin–streptavidin couple generates one of the strongest biological interactions and can serve as an effective model system in the study of a novel biosensing platform.…”

“…The aim of this work is to compare the functionalization strategies resulting in the 3MPA:11MUA and NMPA:11MUA mixed SAMs in terms of sensing performance. The literature on amide-based hydrogen bonds within SAMs is rather limited − despite the fact that it has been proven that SAMs bearing amide moieties lead to more robust and stable surfaces suitable for further modification and biofunctionalization . This work provides further compelling evidence of the validity of such an approach with the support of several characterization tools.…”