Formation Kinetics of Mixed Self-Assembled Monolayers of Alkanethiols on GaAs(100)

Abstract

We report on the formation kinetics of mixed self-assembled monolayers (SAMs) comprising 16-mercaptohexadecanoic acid (MHDA) and 11-mercapto-1-undecanol (MUDO) thiols on GaAs(100) substrates. These compounds were selected for their potential in constructing highly selective and efficient architectures for biosensing applications. The molecular composition and quality of one-compound and mixed SAMs were determined by the Fourier transform infrared absorption spectroscopy measurements. The formation of enhanced-quality mixed SAMs was investigated as a function of the molecular composition of the thiol mixture and the proportion of ethanol/water solvent used during their arrangement. Furthermore, the formation of mixed SAMs has been carried out by successive immersion of MHDA SAMs in MUDO thiol solutions and MUDO SAMs in MHDA thiol solution through the process involving thiol-thiol substitution. Our results, in addition to confirming that water-ethanol-based solvents improve the packing density of single thiol monolayers, demonstrate the attractive role of water-ethanol solvents in forming superior quality mixed SAMs.

In Situ Monitoring of Alkanethiol Self‐Assembly onto Zinc Selenide: The Role of Substrate Pretreatment and Its Implication in Bacterial Attachment

“…The obtained values are overall in the same range as those found in the study of Lacour et al describing the adsorption of alkanethiols onto gallium arsenide (A ads = 0.51, τ ads = 0.11, and τ rea = 2.62). [36] The data on the kinetics of SAM formation and surface coverage were in good agreement with the organization of the SAM estimated from the position of νCH 2 bands (Figure 4b). Indeed, the lower wavenumber of ν asym CH 2 band of the SAM on Au/ ZnSe compared to ZnSe suggests a lower number of conformational defects on the former surface.…”

“…The experimental values shown in Figure 4a were fitted using Equation (1) of Langmuir adsorption and rearrangement model (r 2 ≥ 0.95): [36] A A A e A e…”

Recent advances in surface chemistry of electrodes to promote direct enzymatic bioelectrocatalysis

“…All-atom molecular dynamic simulation confirms the electrostatic model for BOD, and highlights preserved conformation of the enzyme in the immobilized state [11]. Mixed SAMs can be used to tune the number of surface functionalities and their distribution [12]. Covalent immobilization can be realized by amide coupling between corresponding carboxylic and amine functions on the enzyme and the SAM.…”

Mixed‐monolayer of N‐hydroxysuccinimide‐terminated cross‐linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

“…In addition to their spontaneous and controllable formation in an oriented manner, they are easily characterized by contact angle measurements and various spectroscopic tools . mSAMs generated by attachment of two different molecules increases the functionality of the surface by bringing together the chemical structure properties of two components in one platform . Short‐chain hydroxyl‐terminated alkanethiols when immobilized together with biological recognition of interest, decrease the density of the biological recognition elements on the surface and hence act as ‘diluents’.…”

“…5,9,[13][14][15][16][17] mSAMs generated by attachment of two different molecules increases the functionality of the surface by bringing together the chemical structure properties of two components in one platform. 18 Shortchain hydroxyl-terminated alkanethiols when immobilized together with biological recognition of interest, decrease the density of the biological recognition elements on the surface and hence act as 'diluents'.…”